Corundum in a sentence

A hardness of 7 indicates that rose quartz is capable of scratching glass and softer minerals, but it can still be scratched by harder materials like corundum (which includes sapphires and rubies) and diamond.

Amazon.com makes up about 0.8% of Corundum Group Inc.’s investment portfolio, making the stock its 25th biggest position.

Corundum Group Inc.’s holdings in Microsoft were worth $3,365,000 as of its most recent filing with the Securities & Exchange Commission.

We learn, too, of the Mohs Scale that judges hardness, a logarithmic affair where diamond (at the top, scoring 10) can scratch corundum (nine) all the way down to talc (one).

The ruby is the red form of the corundum and, after the diamond, is the next hardest gemstone.

After the 18th century the word ruby was only used for the red gem variety of the mineral corundum and the word spinel came to be used.

All other hues of the gem species corundum are called sapphire.

Among the natural gems only moissanite and diamond are harder, with diamond having a Mohs hardness of 10.0 and moissanite falling somewhere in between corundum (ruby) and diamond in hardness.

Because of the simplicity of the methods involved in corundum synthesis, large quantities of these crystals have become available on the market causing a significant reduction of price in recent years.

Dark blue sapphire, probably of Australian origin, showing the brilliant surface luster typical of faceted corundum gemstones.

For example, ruby and sapphire have the same chemical composition (both are corundum ) but exhibit different colors.

For softer materials silicon carbide, garnet (emery) or corundum can be used in place of the diamond.

Four corundum axes dating back to 2500 BCE from the Liangzhou culture have been discovered in China.

Hydrothermal lab-grown alexandrite has identical physical and chemical properties to real alexandrite. citation Some gemstones falsely described as lab-grown synthetic alexandrite are actually corundum laced with trace elements (e.

In 1877 Frenic and Freil made crystal corundum from which small stones could be cut.

In the lattice of corundum, the oxygen atoms form a slightly distorted hexagonal close packing in which two thirds of the gaps between the octahedra are occupied by aluminum ions.

Likewise, the only difference between ruby and sapphire is the type of impurities present in a corundum crystal.

Sapphire and ruby are impure corundum contaminated with trace amounts of other metals.

Structure and physical properties Crystal structure of corundum Molar volume vs. pressure at room temperature.

The largest documented single crystal of corundum measured about convert, and weighed convert. citation The record has since been surpassed by certain synthetic boules.