Ruby is a variety of corundum with a characteristic bright red color.
Color: Different shades of red
Density: 3.97 to 4.05
Ruby gets its name from its red color. Only in the 1800s was it discovered that rubies and sapphires are two different varieties of the mineral corundum. Before that time, a ruby was known as both a red spinel and a garnet. The main chromophore in a ruby is chromium, with brownish hues given by iron. The color of a ruby varies from deposit to deposit, as well as within a single deposit; therefore, it is impossible to judge where it came from by its hue. The coloring is often distributed unevenly, either in spots or stripes. The untreated stones show a low or very greasy shine, but a cut ruby sparkles almost like a diamond.
In hardness, ruby, like corundum in general, is second only to diamond, though it is 140 times softer. But a ruby is 7 times harder than topaz, the next best reference mineral on the Mohs scale.
Inclusions that are often found in rubies testify to their natural origin. The nature of the inclusions (minerals, channels, or other cavities) can give an indication of the ruby's origin. Inclusions of rutile needles give the stone a delicate, silky sheen, or, when the cabochon is given a proper polishing, a cat's-eye effect, or they give the highly valued asterism, the figure of a six-ray star that slides over the surface of the cabochon when the stone is turned.
Main deposits: Burma, Sri Lanka, Thailand, India, Kampuchea, Vietnam, Tanzania, Australia.
The classical cut for rubies, like for sapphires, is the 57 faceted oval cut (Ov-57). The cabochon cut is often used for stones that are not completely transparent or opaque, as well as for stones with a star effect (asterism). In terms of the Ov-57 cut, all other brilliant cuts for rubies are fantasy cuts.
Color Group Assessment of Ruby
|2||Medium-red and normal-red|
Cleanliness assessment of Ruby
|1||Clean and with insignificant defects in the form of rare cracks, strips, and dotted inclusions in various areas of the stone. They have a luster.||With defects in the form of cracks, stripes, and inclusions with areas of turbidity in different areas of the stone that have partially lost their luster and play.|
|2||With small imperfections in the form of cracks, stripes, combined with pinpoint inclusions of other minerals, which form clumps or networks in certain areas of the stone. They have a luster.||With large defects in the form of a dense network of cracks, strips, and inclusions with zones of turbidity in the stone volume. Semitransparent and opaque, having partially lost their luster and play.|
|3||Defects in the form of cracks, striations, spot inclusions of other minerals all over the stone, patches of turbidity in certain areas of the stone, and partial loss of luster.|
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