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B1 noun #47 mais comum 12 min de leitura

corundums

Top 47

Pratique Exemplos Notas e dicas corundums em 30 segundos

Explicação corundums in your Level:

Corundums are very hard stones. They are like rocks that come in many pretty colors. The most famous ones are red and blue. We call the red ones 'rubies' and the blue ones 'sapphires.' These stones are so hard that they are hard to scratch. People use them to make beautiful rings and necklaces. You might see them in a museum or a jewelry shop. Even though they have a difficult name, you can just think of them as 'very hard, colorful gemstones.' They are found deep in the ground. Because they are so tough, they stay beautiful for a long time. Some people also use them in machines because they don't break easily. Imagine a stone that is almost as hard as a diamond—that is what a corundum is. They are special because they are both useful and pretty. You can find them in many countries around the world. When you see a red ruby, you are looking at a corundum. When you see a blue sapphire, you are also looking at a corundum. They are like brothers and sisters in the same stone family. Learning about them is fun because they are some of the most famous stones in the world.

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Corundums are a type of mineral that is famous for being very hard and colorful. In the world of science, they are made of aluminum and oxygen. But most people know them as rubies and sapphires. If you find a red corundum, it is a ruby. If it is blue, yellow, or pink, it is a sapphire. These stones are very important because they are the second hardest natural material on Earth. Only diamonds are harder. This means that corundums are great for jewelry because they don't get scratched easily by everyday things. You can wear a sapphire ring for many years, and it will still look new. Besides jewelry, corundums are used in industry. Because they are so hard, they are ground into small pieces to make sandpaper. This sandpaper is used to smooth down metal or wood. You might also find tiny corundums inside expensive watches. They act as small parts that help the watch move smoothly without wearing out. So, corundums are not just for looking pretty; they are also very useful in technology. When you hear the word 'corundums,' think of hard, colorful crystals that can be found in rings or in machines.

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Corundums are crystalline forms of aluminum oxide that are exceptionally durable and versatile. In the field of gemology, corundum is the species name for two of the most popular gemstones: rubies and sapphires. The distinction between them is based entirely on color, which is caused by small amounts of impurities like chromium or iron. For example, chromium gives rubies their iconic red hue, while a combination of iron and titanium creates the classic blue of a sapphire. Beyond their aesthetic appeal, corundums are highly valued for their physical properties. On the Mohs scale of mineral hardness, they rank at a 9, making them much harder than quartz or glass. This extreme hardness makes them ideal for industrial uses, such as creating abrasives for grinding and polishing. You will often find 'emery,' a natural mixture of corundum and other minerals, used in workshops. Additionally, synthetic corundums are widely produced in laboratories. These man-made stones are used in everything from the 'jewel' bearings in mechanical watches to the scratch-resistant glass on high-end smartphones. Whether natural or synthetic, corundums play a significant role in both the luxury market and modern engineering, making them a fascinating subject for anyone interested in Earth sciences or technology.

Corundums represent a significant category of minerals known as aluminum oxides ($Al_2O_3$). They are characterized by their trigonal crystal system and their remarkable hardness, which is a defining feature used for identification. In the gemstone industry, the term 'corundums' serves as an umbrella for rubies and sapphires. The presence of trace elements within the crystal lattice determines the stone's variety; for instance, chromium ions replacing aluminum ions result in the red color of a ruby. Any other color—ranging from the traditional blue to yellow, green, and even 'colorless'—is classified as a sapphire. This mineral's industrial importance cannot be overstated. Due to its Mohs hardness of 9, it is a primary component in abrasives like sandpaper and grinding wheels. Furthermore, the development of synthetic corundums via the Verneuil or Czochralski processes has allowed for the mass production of high-quality crystals for technological applications. These include laser rods, watch bearings, and specialized windows for spacecraft and high-pressure environments. When discussing corundums, it is essential to distinguish between the natural specimens found in metamorphic or igneous rocks and the synthetic versions used in industry. The word is frequently used by geologists to describe the mineralogy of specific regions, such as the gem-rich gravels of Sri Lanka or the basaltic deposits of Australia. Understanding corundums requires an appreciation of both their chemical simplicity and their diverse physical manifestations.

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Corundums, the crystalline iterations of anhydrous aluminum oxide, occupy a prestigious position in both mineralogy and material science due to their extraordinary physical and chemical stability. Crystallizing in the rhombohedral system, these minerals exhibit a density and hardness that are surpassed only by diamonds and a few rare synthetic materials. The gemological distinction between rubies and sapphires is a matter of trace element substitution; the 'pigeon-blood' red of a ruby is the result of $Cr^{3+}$ ions, while the deep blue of a sapphire arises from intervalence charge transfer between $Fe^{2+}$ and $Ti^{4+}$. Beyond the aesthetic allure of these gemstones, corundums are indispensable in high-tech industries. The production of synthetic corundums has facilitated the creation of 'sapphire glass,' a highly scratch-resistant material used in premium horology and aerospace engineering. In the realm of optics, synthetic corundums serve as the medium for various solid-state lasers, most notably the ruby laser, which was the first of its kind. Furthermore, the industrial application of corundums as abrasives—often referred to as 'alumina' in its calcined form—is vital for precision machining and the manufacturing of refractory materials. When analyzing corundums in a geological context, they are often found as accessory minerals in silica-poor rocks, such as nepheline syenites or within contact metamorphic zones. The study of corundums thus offers profound insights into the geochemical processes that govern the formation of the Earth's crust and the development of advanced synthetic materials that drive modern innovation.

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The term 'corundums' encompasses a suite of aluminum oxide minerals ($Al_2O_3$) that represent the pinnacle of durability and structural integrity within the oxide class. From a crystallographic perspective, corundums belong to the $R\bar{3}c$ space group, characterized by a hexagonal close-packed arrangement of oxygen anions with aluminum cations occupying two-thirds of the octahedral interstices. This robust lattice structure accounts for the mineral's exceptional Mohs hardness of 9 and its high refractive index, which contributes to the 'fire' and brilliance observed in faceted specimens. The nomenclature of corundums is deeply bifurcated between scientific classification and commercial gemology. While a mineralogist views them through the lens of lattice defects and trace element concentrations—such as the role of vanadium in color-change varieties—the market categorizes them by hue, saturation, and tone. The industrial synthesis of corundums, particularly through the flux growth and hydrothermal methods, has pushed the boundaries of material science, enabling the fabrication of large-scale, high-purity crystals for use in semiconductor substrates and high-energy laser systems. Moreover, the study of corundums extends into the domain of geochronology and petrology, where the presence of corundum-bearing xenoliths provides critical data regarding the thermal and baric conditions of the upper mantle and lower crust. In professional discourse, 'corundums' is used with a precision that acknowledges the mineral's multifaceted utility—from the abrasive grit essential for metallurgical polishing to the 'jewel' bearings that mitigate frictional torque in chronometers. Thus, the word 'corundums' serves as a linguistic bridge connecting the primordial geological forces of the Earth with the sophisticated frontiers of contemporary quantum electronics and aerospace technology.

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Pratique Exemplos Notas e dicas

corundums em 30 segundos

Corundums are the mineral family that includes rubies and sapphires, known for extreme hardness.
They are made of aluminum oxide and rank 9 on the Mohs scale of mineral hardness.
Used extensively in both high-end jewelry and industrial abrasive applications like sandpaper.
Synthetic versions are common in technology, including watch bearings and scratch-resistant screens.

When we talk about corundums, we are stepping into the fascinating world of mineralogy and high-end jewelry. At its simplest, corundum is a crystalline form of aluminum oxide. However, in common parlance, we rarely use the technical term unless we are discussing the broad category of stones that include the world's most famous gems. Corundums are the parent species for both rubies and sapphires. If a corundum is red, it is a ruby; if it is any other color, it is a sapphire. This distinction is vital for collectors, geologists, and jewelers alike. People use this word when they need to describe the physical properties of these stones collectively, particularly their extreme hardness, which is second only to diamonds on the Mohs scale. This hardness makes them indispensable not just for adornment, but for heavy-duty industrial applications.

Mineralogical Classification: Corundums belong to the hematite group and crystallize in the trigonal system, often forming barrel-shaped or hexagonal crystals that are remarkably dense.

The museum's latest exhibit showcases a rare collection of untreated corundums sourced from the riverbeds of Myanmar.

In industrial contexts, the term is used to refer to abrasives. Because corundums are so tough, they are ground into powders to create sandpaper, grinding wheels, and cutting tools. You might hear a machinist talk about the longevity of their tools being due to the high concentration of synthetic corundums used in the coating. Unlike the gemstones found in a necklace, industrial corundums are often manufactured in labs to ensure consistency and lower costs. Whether natural or synthetic, the defining characteristic remains the same: an unyielding resistance to scratching and wear. This dual nature—being both a symbol of luxury and a workhorse of industry—makes the study of corundums a unique intersection of art and engineering.

Industrial Utility: Due to their Mohs hardness of 9, corundums are the standard material for testing the scratch resistance of other minerals and glass types.

Geologists identified the rock samples as metamorphic schists containing small, embedded corundums.

Furthermore, the word appears frequently in discussions about synthetic gemstone production. The Verneuil process, developed in the late 19th century, allowed for the creation of large, flawless corundums in a laboratory setting. This revolutionized the watchmaking industry, where tiny corundums—often called 'jewels'—are used as low-friction bearings for the delicate moving parts of mechanical watches. When you see a watch advertised as having '21 jewels,' it is almost certainly referring to these synthetic corundums. This application highlights the word's relevance in high-precision technology, where the physical properties of the material are more important than its aesthetic beauty.

Color Variations: The presence of chromium creates red corundums (rubies), while iron and titanium result in blue corundums (sapphires).

Abrasive papers coated with crushed corundums are essential for polishing hardened steel surfaces.

The durability of corundums ensures that ancient artifacts made from these stones remain perfectly preserved.

Investors often look for high-clarity corundums as a hedge against inflation in the gemstone market.

Using the word corundums correctly requires an understanding of whether you are speaking from a scientific, industrial, or artistic perspective. In a scientific context, it is treated as a plural noun referring to multiple specimens or types of the mineral. For example, you might say, 'The geological survey identified several distinct corundums within the basaltic flow.' Here, the plural form emphasizes the variety or the individual crystals found. It is important to note that while 'corundum' is often used as an uncountable noun (like 'sand' or 'water'), the plural 'corundums' is specifically used when referring to different varieties or specific individual stones.

Geological Context: When describing the formation of rocks, use 'corundums' to specify the presence of these crystals as secondary minerals in metamorphic environments.

The laboratory synthesized several corundums to test their thermal conductivity at extreme temperatures.

In the jewelry trade, the plural form is less common than the specific names of the stones (rubies and sapphires), but it is used when discussing the broad category of stones that share the same chemical structure. A gemologist might write, 'The auction house featured a stunning array of corundums, ranging from deep pigeon-blood rubies to cornflower blue sapphires.' This usage allows the speaker to group these stones together under their shared mineralogical identity while acknowledging their diverse appearances. It sounds more professional and technically accurate than simply saying 'red and blue stones.'

Jewelry Cataloging: Use 'corundums' when you want to emphasize the shared physical properties of rubies and sapphires in a professional report.

Many high-end watches utilize synthetic corundums as pivot points to minimize mechanical friction.

In academic writing, particularly in chemistry or materials science, the word is used to describe the various allotropes or crystalline arrangements of aluminum oxide. A researcher might state, 'The structural integrity of these corundums was analyzed using X-ray diffraction.' This highlights the technical nature of the word. It is also useful in historical accounts of mining. For instance, 'The mines of Ceylon have been famous for their high-quality corundums for over two millennia.' Here, the word provides a sense of historical and scientific weight to the description of the gems.

Academic Precision: In papers, use the plural to refer to different samples of the mineral collected from various geographical locations.

The artisan preferred using natural corundums over synthetic ones to give the jewelry a more organic feel.

Because corundums are so chemically stable, they are often used in the manufacturing of laboratory equipment.

The jeweler explained that the 'star' effect in certain corundums is caused by needle-like inclusions of rutile.

You are most likely to encounter the word corundums in specialized environments rather than in everyday casual conversation. One of the primary places is a geology or mineralogy museum. Curators use the term to categorize their collections, often placing rubies and sapphires in the same display case under the label 'Corundums.' If you take a guided tour, the docent might explain how these crystals form deep within the Earth's crust under intense heat and pressure. Hearing the word in this context emphasizes its scientific classification and its relationship to other minerals like quartz or beryl.

Museum Exhibits: Educational signage often uses 'corundums' to explain the chemical unity behind seemingly different gemstones.

The professor noted that the volcanic pipe contained several large corundums of varying clarity.

Another common setting is the high-end jewelry industry, specifically during the appraisal or wholesale process. While a customer in a retail store might only hear 'ruby' or 'sapphire,' a gemologist behind the scenes will use 'corundums' when discussing the quality of a shipment. They might say, 'This batch of corundums has excellent saturation but needs better cutting.' In this professional sphere, the word acts as a technical shorthand that encompasses all color varieties. It is also heard in gemstone cutting (lapidary) workshops, where the hardness of the material dictates the type of diamond-tipped tools required to shape it.

Gemological Labs: Technicians use the term when performing spectroscopic analysis to identify the origin of the stones.

During the lecture, we learned that the hardness of corundums makes them ideal for industrial sandblasting.

In the world of watchmaking and precision engineering, 'corundums' is a standard term. If you visit a factory that produces mechanical timepieces, you will hear engineers discussing the placement of synthetic corundums in the movement. These 'jewels' are essential for the watch's accuracy and longevity. Similarly, in advanced manufacturing, you might hear about 'corundum-coated' components designed to withstand high friction. This industrial usage is perhaps the most frequent way the word is heard outside of the gem world, highlighting its role as a high-performance material in modern technology.

Watchmaking Industry: The term 'jewel count' in watches almost always refers to the number of synthetic corundums used as bearings.

The jeweler's loupe revealed tiny fractures in the corundums, indicating they had been heat-treated.

Archaeologists found ancient beads made of polished corundums in the burial chamber.

The abrasive manufacturer offers a variety of corundums for different metal-finishing tasks.

One of the most frequent mistakes people make with the word corundums is failing to realize that rubies and sapphires are actually the same mineral. Many people treat 'ruby,' 'sapphire,' and 'corundum' as three entirely different substances. It is important to remember that corundum is the category, while ruby and sapphire are the specific varieties. Another common error is the misspelling of the word, often confusing it with 'conundrum' (a confusing problem). While they sound somewhat similar, they have completely different meanings. A conundrum is a puzzle; a corundum is a rock. Mixing these up in writing can lead to significant confusion, especially in academic or professional settings.

Spelling Confusion: Do not confuse 'corundum' (the mineral) with 'conundrum' (a puzzle or difficult question).

The student mistakenly wrote about 'geological conundrums' when they meant to discuss the properties of corundums.

Another mistake involves the pluralization of the word. In many scientific contexts, 'corundum' is used as an uncountable mass noun. However, when referring to specific individual crystals or different types of the mineral, 'corundums' is the correct plural form. Some writers mistakenly use 'corundum' when they should use 'corundums' to indicate plurality. For example, saying 'the collection consisted of many corundum' is grammatically incorrect; it should be 'many corundums.' Additionally, people often forget that corundums come in almost every color of the rainbow. While rubies are red, sapphires can be blue, yellow, pink, green, or even colorless. Using 'corundums' is the best way to encompass all these variations without having to list every color.

Plural vs. Singular: Use 'corundum' for the material in general and 'corundums' for specific stones or varieties.

Identifying corundums solely by color is a mistake, as many minerals can mimic their appearance.

Finally, there is often confusion regarding the hardness of corundums compared to diamonds. While corundums are extremely hard (Mohs 9), they are significantly softer than diamonds (Mohs 10). In fact, a diamond is about four times harder than a corundum. People sometimes mistakenly claim that corundums are the hardest substance on Earth, which is incorrect. This distinction is crucial in both jewelry care and industrial applications. You can use diamond dust to polish corundums, but you cannot use corundum dust to polish diamonds. Understanding this hierarchy of hardness is essential for anyone working with these materials.

Hardness Hierarchy: Remember: Diamonds > Corundums > Most other minerals. Corundums are hard, but not the hardest.

The engineer corrected the report, noting that corundums would be scratched by diamond-tipped drills.

It is a common error to assume that all red corundums are of equal value; clarity and origin play huge roles.

The lapidary warned that synthetic corundums can sometimes be mistaken for natural ones without proper testing.

When exploring the vocabulary related to corundums, it is helpful to look at both scientific synonyms and common gemstone names. The most direct scientific alternative is 'aluminum oxide,' though this term is usually reserved for the chemical compound rather than the mineral form. In industrial contexts, 'emery' is a very close relative. Emery is a rock that consists primarily of corundum mixed with other minerals like magnetite or hematite. While not as pure as the corundums used in jewelry, emery is the term you will most often see on heavy-duty sandpaper and abrasive products. Understanding the link between these words helps bridge the gap between science and everyday utility.

Emery vs. Corundum: Emery is an impure, granular variety of corundum used almost exclusively for industrial grinding and polishing.

While the jeweler sold rubies, the hardware store sold emery boards, both of which are essentially corundums.

In the world of gemstones, the most common alternatives are 'rubies' and 'sapphires.' As mentioned before, these are specific types of corundums. If you are writing for a general audience, using 'rubies and sapphires' is often more effective than using the technical term 'corundums.' However, if you need to describe a stone that is neither red nor blue—such as a yellow or pink variety—you might use the term 'fancy sapphires' or 'colored corundums.' Another related term is 'padparadscha,' which is a rare and highly prized pink-orange variety of corundum. These specific names provide more detail and color to your descriptions than the broad category name.

Fancy Sapphires: This term is used for all gem-quality corundums that are not red (rubies) or blue (traditional sapphires).

The collector's vault contained several rare corundums, including a prized padparadscha from Sri Lanka.

From a technical standpoint, 'alumina' is another word often used interchangeably with corundum in manufacturing. Alumina is the chemical name for aluminum oxide ($Al_2O_3$). In ceramic engineering, you will hear about 'alumina ceramics,' which are essentially synthetic corundums used for their electrical insulation and heat resistance. While 'corundum' sounds more natural and geological, 'alumina' sounds more industrial and chemical. Depending on your audience, choosing between these words can change the tone of your communication from 'natural wonder' to 'engineered material.' Knowing these nuances allows for much more precise and effective communication.

Alumina: The chemical term for the substance that makes up corundums, used frequently in engineering and chemistry.

High-purity alumina is used to grow the large corundums used in smartphone camera lenses.

The geologist compared the corundums to other oxide minerals like spinel and chrysoberyl.

Because of their similar density, some garnets can be mistaken for red corundums by the untrained eye.

How Formal Is It?

Curiosidade

Despite being the same mineral, rubies were once thought to be completely unrelated to sapphires until chemical analysis in the late 1700s proved they were both corundums.

Guia de pronúncia

UK /kəˈrʌndəmz/

US /kəˈrʌndəmz/

Second syllable (co-RUN-dums)

Rima com

conundrums humdrums drums sums comes plums thums gums

Erros comuns

Pronouncing it like 'conundrum' (co-NUN-drum).
Putting the stress on the first syllable.
Pronouncing the 'u' as a long 'oo' sound.
Adding an extra 'i' (corundium).
Muffling the final 'z' sound in the plural.

Nível de dificuldade

Leitura 4/5

Requires some scientific or gemological context to understand fully.

Escrita 5/5

Easy to confuse with 'conundrum' if not careful with spelling.

Expressão oral 3/5

Pronunciation is straightforward once the stress is learned.

Audição 4/5

Can be easily misheard in fast speech due to the schwa sounds.

O que aprender depois

Pré-requisitos

Mineral Crystal Hardness Oxide Gemstone

Aprenda a seguir

Beryl Topaz Refractive index Inclusions Mohs scale

Avançado

Pleochroism Asterism Allochromatic Trigonal system Verneuil process

Gramática essencial

Pluralization of scientific terms

Corundums (plural) vs Corundum (mass noun).

Compound adjectives with hyphens

Corundum-tipped drills.

Using 'the' with specific groups

The corundums in this display are from Africa.

Passive voice in technical descriptions

Corundums are formed under high pressure.

Appositives for definitions

Corundums, a type of aluminum oxide, are very hard.

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Exemplos por nível

I saw many red corundums in the museum.

J'ai vu beaucoup de corindons rouges au musée.

Plural noun 'corundums' used with 'many'.

Corundums are very hard stones.

Les corindons sont des pierres très dures.

Simple subject-verb-object structure.

The blue corundums are called sapphires.

Les corindons bleus sont appelés saphirs.

Passive voice 'are called'.

Can you find the corundums in this box?

Peux-tu trouver les corindons dans cette boîte ?

Question form using 'can'.

These corundums are very pretty.

Ces corindons sont très jolis.

Demonstrative adjective 'these'.

She has a ring with small corundums.

Elle a une bague avec de petits corindons.

Prepositional phrase 'with small corundums'.

Corundums come from the ground.

Les corindons viennent du sol.

Present simple tense for a general fact.

I like the yellow corundums best.

J'aime le plus les corindons jaunes.

Adverb 'best' modifying the verb 'like'.

The jeweler showed us different corundums.

Le bijoutier nous a montré différents corindons.

Past simple tense 'showed'.

Because corundums are hard, they do not scratch.

Parce que les corindons sont durs, ils ne se rayent pas.

Subordinating conjunction 'because'.

You can use crushed corundums to polish metal.

On peut utiliser des corindons broyés pour polir le métal.

Modal verb 'can' followed by an infinitive.

Are all corundums expensive?

Est-ce que tous les corindons sont chers ?

Interrogative sentence with 'are'.

He found some corundums while hiking in the mountains.

Il a trouvé des corindons en faisant de la randonnée en montagne.

Past continuous 'while hiking' used with past simple.

The watch has twenty-one synthetic corundums inside.

La montre contient vingt et un corindons synthétiques à l'intérieur.

Adjective 'synthetic' modifying 'corundums'.

Corundums are found in many parts of the world.

On trouve des corindons dans de nombreuses parties du monde.

Passive voice 'are found'.

My teacher explained that rubies are actually corundums.

Mon professeur a expliqué que les rubis sont en réalité des corindons.

Reported speech with 'that'.

The hardness of corundums makes them ideal for industrial use.

La dureté des corindons les rend idéaux pour un usage industriel.

Subject-verb agreement: 'hardness' (singular) takes 'makes'.

Scientists can create synthetic corundums in a laboratory.

Les scientifiques peuvent créer des corindons synthétiques dans un laboratoire.

Adjective 'synthetic' used to distinguish from 'natural'.

If you look closely, you can see the crystal structure of these corundums.

Si vous regardez de près, vous pouvez voir la structure cristalline de ces corindons.

First conditional: 'If you look... you can see'.

Corundums are often heat-treated to improve their color and clarity.

Les corindons sont souvent traités thermiquement pour améliorer leur couleur et leur clarté.

Compound noun 'heat-treated'.

The exhibition featured a variety of corundums from Sri Lanka.

L'exposition présentait une variété de corindons provenant du Sri Lanka.

Prepositional phrase 'from Sri Lanka'.

Unlike diamonds, corundums are composed of aluminum oxide.

Contrairement aux diamants, les corindons sont composés d'oxyde d'aluminium.

Contrastive transition 'unlike'.

Many ancient civilizations valued corundums for their beauty and strength.

De nombreuses civilisations anciennes appréciaient les corindons pour leur beauté et leur force.

Past simple 'valued'.

The price of corundums depends on their size and quality.

Le prix des corindons dépend de leur taille et de leur qualité.

Verb 'depends on' followed by a noun phrase.

The geological report confirmed the presence of corundums in the metamorphic rock.

Le rapport géologique a confirmé la présence de corindons dans la roche métamorphique.

Use of technical term 'metamorphic rock'.

Corundums are frequently used as abrasives in the manufacturing of precision tools.

Les corindons sont fréquemment utilisés comme abrasifs dans la fabrication d'outils de précision.

Adverb 'frequently' modifying the passive verb.

While rubies are always red, other corundums can be found in a spectrum of colors.

Alors que les rubis sont toujours rouges, d'autres corindons peuvent être trouvés dans un spectre de couleurs.

Concessive clause starting with 'while'.

The synthetic corundums used in watches are often referred to as 'jewels'.

Les corindons synthétiques utilisés dans les montres sont souvent appelés 'rubis'.

Reduced relative clause: '(which are) used in watches'.

Identifying natural corundums requires careful examination of their inclusions.

L'identification des corindons naturels nécessite un examen attentif de leurs inclusions.

Gerund 'identifying' as the subject.

The durability of corundums makes them suitable for high-friction environments.

La durabilité des corindons les rend adaptés aux environnements à friction élevée.

Adjective 'suitable' followed by 'for'.

Investors are increasingly turning to high-quality corundums as a stable asset.

Les investisseurs se tournent de plus en plus vers les corindons de haute qualité comme actif stable.

Present continuous 'are turning' for a current trend.

The chemical formula for all corundums is $Al_2O_3$.

La formule chimique de tous les corindons est $Al_2O_3$.

Preposition 'for' indicating purpose or category.

The spectroscopic analysis revealed that the corundums were of basaltic origin.

L'analyse spectroscopique a révélé que les corindons étaient d'origine basaltique.

Noun clause 'that the corundums were...'.

Corundums exhibit a high refractive index, which accounts for their exceptional brilliance.

Les corindons présentent un indice de réfraction élevé, ce qui explique leur éclat exceptionnel.

Relative clause 'which accounts for...'.

The artisan skillfully faceted the corundums to maximize their light return.

L'artisan a habilement facetté les corindons pour maximiser leur retour de lumière.

Adverb 'skillfully' modifying the verb 'faceted'.

Trace amounts of chromium are responsible for the vibrant red in certain corundums.

Des traces de chrome sont responsables du rouge éclatant de certains corindons.

Subject 'trace amounts' (plural) takes 'are'.

The historical significance of these corundums cannot be overstated in the context of trade.

L'importance historique de ces corindons ne saurait être surestimée dans le contexte du commerce.

Modal passive 'cannot be overstated'.

Synthetic corundums have revolutionized the field of solid-state lasers.

Les corindons synthétiques ont révolutionné le domaine des lasers à solide.

Present perfect 'have revolutionized'.

The mining of corundums often involves processing vast quantities of alluvial gravel.

L'extraction des corindons implique souvent le traitement de vastes quantités de gravier alluvionnaire.

Gerund 'mining' as the subject.

Despite their hardness, corundums can still suffer from brittle fracture under extreme impact.

Malgré leur dureté, les corindons peuvent encore subir une fracture fragile sous un impact extrême.

Preposition 'despite' followed by a noun phrase.

The petrogenesis of corundums within these xenoliths suggests a complex mantle history.

La pétrogenèse des corindons au sein de ces xénolithes suggère une histoire complexe du manteau.

Highly technical vocabulary: 'petrogenesis', 'xenoliths'.

The lattice structure of corundums is characterized by a hexagonal close-packing of oxygen ions.

La structure en réseau des corindons est caractérisée par un empilement hexagonal compact d'ions oxygène.

Passive voice with a complex technical agent.

Corundums serve as critical components in high-pressure physics experiments due to their incompressibility.

Les corindons servent de composants critiques dans les expériences de physique à haute pression en raison de leur incompressibilité.

Prepositional phrase 'due to their incompressibility'.

The pleochroism observed in certain corundums allows gemologists to determine their orientation.

Le pléochroïsme observé dans certains corindons permet aux gemmologues de déterminer leur orientation.

Technical term 'pleochroism' as the subject.

Advanced hydrothermal methods are employed to grow large, flawless corundums for industrial optics.

Des méthodes hydrothermales avancées sont employées pour faire croître de grands corindons sans défaut pour l'optique industrielle.

Passive voice 'are employed'.

The thermodynamic stability of corundums makes them a primary phase in many metamorphic assemblages.

La stabilité thermodynamique des corindons en fait une phase primaire dans de nombreux assemblages métamorphiques.

Complex noun phrase 'thermodynamic stability'.

Inclusions within corundums, such as rutile silk, provide invaluable clues regarding their geographic provenance.

Les inclusions au sein des corindons, telles que la soie de rutile, fournissent des indices inestimables concernant leur provenance géographique.

Appositive phrase 'such as rutile silk'.

The anisotropy of corundums must be accounted for during the precision grinding of optical lenses.

L'anisotropie des corindons doit être prise en compte lors du meulage de précision des lentilles optiques.

Modal passive 'must be accounted for'.

Colocações comuns

Synthetic corundums

Natural corundums

Abrasive corundums

Gem-quality corundums

Heat-treated corundums

Crushed corundums

Untreated corundums

Corundum crystals

White corundums

Brown corundums

Frases Comuns

Hard as corundum

— Extremely hard and difficult to break or scratch.

The new alloy is said to be as hard as corundum.

Corundum-based abrasive

— A tool or material that uses corundum to grind other things.

We need a corundum-based abrasive for this steel polishing job.

Jewel-grade corundums

— Stones that are clear and colorful enough to be used in jewelry.

The mine is famous for producing jewel-grade corundums.

Industrial corundums

— Corundums used for manufacturing rather than decoration.

Industrial corundums are often synthetic to ensure uniform hardness.

Corundum structure

— The specific hexagonal arrangement of atoms in aluminum oxide.

The scientist studied the corundum structure using X-ray diffraction.

Metamorphic corundums

— Corundums formed through the transformation of rocks under heat and pressure.

These metamorphic corundums were found in a marble deposit.

Corundum grit

— Small, sharp particles of corundum used for sandblasting.

The surface was cleaned using a fine corundum grit.

Star corundums

— Stones that show a star-like light pattern (asterism).

Star corundums are highly valued by collectors of rare gems.

Corundum deposits

— Areas in the earth where corundum is found in large amounts.

The government is surveying the region for new corundum deposits.

Calcined corundums

— Corundums that have been heated to high temperatures for industrial use.

Calcined corundums are used in the production of spark plugs.

Frequentemente confundido com

corundums vs Conundrums

A conundrum is a puzzle; a corundum is a mineral. They sound similar but are unrelated.

corundums vs Spinels

Spinels are another type of hard mineral often found with corundums and mistaken for them.

corundums vs Quartz

Quartz is also a common mineral, but it is much softer (Mohs 7) than corundum (Mohs 9).

Expressões idiomáticas

"A diamond in the corundum"

— Something truly exceptional found among other high-quality things.

In this class of bright students, she is a diamond in the corundum.

Literary

"Harder than a corundum's heart"

— Extremely stubborn or emotionally cold.

The negotiator was harder than a corundum's heart and wouldn't budge.

Informal

"To polish a corundum"

— To put a lot of effort into making something already good even better.

The editor spent weeks polishing the corundum of a manuscript.

Metaphorical

"Rough corundums"

— People or things with great potential that need refinement.

These new recruits are rough corundums, but they'll be stars soon.

Business

"The corundum standard"

— A high level of durability or quality.

Their customer service is the corundum standard of the industry.

Professional

"To cut corundum with corundum"

— To use a powerful tool or person to deal with an equally powerful opponent.

In the debate, they had to cut corundum with corundum by hiring a top lawyer.

Formal

"Clear as a corundum"

— Very transparent or easy to understand (referring to high-quality sapphires).

The instructions were as clear as a corundum.

Informal

"To find a corundum in the gravel"

— To discover something valuable in a mundane or messy place.

Finding that vintage car in the barn was like finding a corundum in the gravel.

Informal

"Built like a corundum"

— Very sturdy and difficult to damage.

That old truck is built like a corundum; it never breaks down.

Slang

"Corundum-tough"

— Possessing extreme mental or physical resilience.

The marathon runner showed corundum-tough determination.

Journalistic

Fácil de confundir

corundums vs Conundrum

Phonetic similarity.

A conundrum is an abstract problem; a corundum is a physical mineral.

Solving the mystery was a conundrum, but the ring was made of corundums.

corundums vs Carborundum

Similar sounding and both are abrasives.

Carborundum is silicon carbide (synthetic), while corundum is aluminum oxide.

He used carborundum for the rough cut and corundums for the final polish.

corundums vs Condominiums

Slight phonetic overlap in the first few letters.

Condominiums are buildings; corundums are stones.

The wealthy man lived in a condominium and collected rare corundums.

corundums vs Curriculum

Ending in '-um' and starting with 'C'.

Curriculum is a course of study; corundum is a rock.

The geology curriculum includes a chapter on corundums.

corundums vs Colloquium

Ending in '-um' and starting with 'C'.

A colloquium is an academic meeting; corundum is a mineral.

The scientists held a colloquium to discuss the new corundums.

Padrões de frases

I see [color] corundums.

I see blue corundums.

Corundums are [adjective] stones.

Corundums are hard stones.

Because corundums are [property], they are used for [purpose].

Because corundums are hard, they are used for sandpaper.

While some corundums are [color], others are [color].

While some corundums are red, others are yellow.

The [noun] of corundums is attributed to [scientific reason].

The color of corundums is attributed to trace impurities.

The [technical property] of corundums necessitates [action].

The anisotropy of corundums necessitates careful orientation during cutting.

Academic

Analysis of the corundums revealed [finding].

Analysis of the corundums revealed high concentrations of iron.

Professional

We recommend using [type] corundums for [task].

We recommend using synthetic corundums for the bearing surfaces.

Família de palavras

Substantivos

Corundum

Alumina

Sapphire

Ruby

Adjetivos

Corundine

Adamantine

Relacionado

Mineralogy

Abrasive

Gemology

Oxide

Crystalline

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Como usar

frequency

Low in daily life, high in geology and jewelry trade.

Erros comuns

Thinking rubies and corundums are different things. → Rubies are a type of corundum.
A ruby is simply a red corundum. They are the same mineral species, just with different trace elements.
Spelling it 'conundrum'. → Corundum.
A conundrum is a puzzle. A corundum is a mineral. They are often confused because they sound similar.
Saying corundums are the hardest material. → Corundums are the second hardest natural material.
Diamonds are harder than corundums. Corundums are a 9 on the Mohs scale, while diamonds are a 10.
Using 'corundum' as a plural for multiple stones. → Corundums.
When referring to individual crystals or a variety of stones, the plural 'corundums' should be used.
Assuming all corundums are expensive. → Only gem-quality corundums are expensive.
Industrial corundums used for sandpaper and grinding are very cheap and produced in large quantities.

Dicas

Use for Grouping

Use 'corundums' when you want to talk about rubies and sapphires together as a single category. It makes your writing sound more professional and scientifically accurate.

The 'U' Sound

Remember that 'corundum' has two 'u's. Think of it as 'Cor-un-dum'. This will help you avoid spelling it like 'conundrum' or adding extra letters like 'i'.

Industrial vs. Gem

Always clarify if you are talking about industrial corundums or gemstones. The price and use are completely different, so adding an adjective helps the reader understand your point.

Formula Fact

If you are in a chemistry class, remember $Al_2O_3$. That is the formula for all corundums. Knowing this can help you understand why they are called 'aluminum oxides' in textbooks.

Hardness Test

If a stone can scratch glass but cannot be scratched by a steel file, it might be a corundum. However, never perform this test on jewelry as it can damage the stone or the setting!

Tamil Roots

Knowing that the word comes from the Tamil word for 'ruby' can help you remember that rubies are the primary member of the corundum family.

Fancy Sapphires

When you encounter the term 'fancy sapphires,' remember it just means corundums that are any color except blue or red. This is a common term in the gem trade.

Watch Jewels

When you see '21 Jewels' on a watch, don't expect real rubies. They are almost always synthetic corundums used for their low friction and high durability.

Ancient Abrasives

Remember that corundums have been used for thousands of years. Ancient civilizations used them to carve harder stones, showing that their industrial value is as old as their beauty.

Plurality

Use 'corundums' (plural) when referring to a collection of different stones. Use 'corundum' (singular) when referring to the mineral species or the material in general.

Memorize

Mnemônico

Think of a 'CORE' that is 'UN'-'DUM' (undumb/smart) because it is so hard and brilliant. Corundums are the core of hard gemstones.

Associação visual

Imagine a red ruby and a blue sapphire sitting on a piece of rough sandpaper. All three are made of corundums.

Word Web

Ruby Sapphire Hardness Mohs 9 Aluminum Oxide Abrasive Sandpaper Watch Jewels

Desafio

Try to find three items in your house that might use corundums (hint: look at sandpaper, nail files, or mechanical watches).

Origem da palavra

The word comes from the Tamil word 'kurundam' or the Sanskrit 'kuruvinda', both meaning 'ruby'. It entered English in the 18th century as trade with India increased. The term was adopted by mineralogists to describe the entire species of aluminum oxide minerals.

Significado original: Ruby or very hard stone.

Indo-Aryan / Dravidian roots via Latin/French.

Contexto cultural

Be aware of 'conflict gems'; ensure that when discussing natural corundums, ethical sourcing is often a point of concern.

Commonly associated with 40th (ruby) and 45th (sapphire) wedding anniversaries.

The 'Black Prince's Ruby' in the British Crown Jewels (actually a spinel, but long mistaken for a corundum). The 'Star of India' sapphire in the American Museum of Natural History. The 'Logan Sapphire' in the Smithsonian Institution.

Pratique na vida real

Contextos reais

Geology Class

Mohs scale of 9
Metamorphic origin
Hexagonal crystals
Aluminum oxide composition

Jewelry Store

Heat-treated stones
Natural vs synthetic
Pigeon-blood red
Cornflower blue

Industrial Workshop

Abrasive grit
Grinding wheel
Polishing compound
Surface finishing

Watchmaking

Jewel bearings
Low friction
Synthetic sapphire crystal
Mechanical movement

Museum Tour

Rare specimens
Untreated gems
Geological history
Mineral species

Iniciadores de conversa

"Did you know that rubies and sapphires are actually the same mineral called corundums?"

"Have you ever seen a watch that uses synthetic corundums as bearings?"

"Why do you think corundums are so much harder than most other rocks?"

"If you could have a collection of corundums, which color would you choose?"

"How do you think scientists tell the difference between natural and synthetic corundums?"

Temas para diário

Describe a piece of jewelry made of corundums that you would like to own and why.

Explain the importance of corundums in modern technology beyond just being pretty stones.

Imagine you are a geologist who has just discovered a new deposit of corundums. Describe your find.

Compare the use of corundums in ancient times versus their use in the modern world.

Write about a 'conundrum' you had that was as 'hard' to solve as a corundum.

Perguntas frequentes

10 perguntas

No, not all corundums are gem-quality. Many are opaque, dull, or heavily fractured, making them unsuitable for jewelry. These 'industrial corundums' are instead used as abrasives or in manufacturing processes where their hardness is useful but their appearance doesn't matter.

The only difference is the color. Both are corundums. If the stone is red, it is called a ruby. If it is any other color (blue, yellow, pink, etc.), it is called a sapphire. This distinction is purely based on the trace elements present in the crystal.

Corundums have a hardness of 9 on the Mohs scale. This makes them the second hardest natural mineral on Earth. Only diamonds, which have a hardness of 10, are harder. This means a corundum can scratch almost any other mineral except a diamond.

Yes, synthetic corundums are produced in large quantities. They have the same chemical and physical properties as natural ones. They are used for jewelry (as a cheaper alternative to natural stones) and for industrial purposes like watch bearings and laser components.

Natural corundums are found all over the world. Famous sources include Myanmar (Burma), Sri Lanka, Madagascar, Thailand, and even parts of the United States like Montana. They are usually found in metamorphic rocks or in river gravels where they have washed down from the mountains.

Some corundums contain tiny, needle-like inclusions of a mineral called rutile. When cut into a dome shape (cabochon), these needles reflect light in a way that creates a six-rayed star pattern on the surface. These are known as star rubies or star sapphires.

The price varies wildly. High-quality, natural rubies and sapphires can be among the most expensive gemstones in the world, sometimes costing thousands of dollars per carat. However, industrial-grade corundums used for sandpaper are very cheap.

Because corundums are so durable, they are easy to clean. You can usually use warm soapy water and a soft brush. They are resistant to most chemicals, but it's always best to avoid harsh acids just in case there are treatments or other stones in the setting.

Many natural corundums are heated to very high temperatures (often over 1500°C) to improve their color and dissolve small inclusions. This is a standard and accepted practice in the jewelry industry, though untreated stones are much rarer and more valuable.

Emery is a rock that contains a high percentage of corundum, but it is mixed with other minerals like magnetite. It is essentially an impure form of corundum. It has been used for centuries as an abrasive for grinding and polishing.

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