The test only identifies the crystal, not the coloration of the crystal as viewed by the human eye. The wide range of colors of sapphires will have no influence on refractive index readings. Each crystal structure will separate light differently and this is one reliable method to identify a crystal structure.Ī refractive index test on a pink, blue, yellow or green sapphire will give the same refractive index reading. Refractive index is the reading of how a crystal separates the spectrum of light. One way to identify a crystal species is by taking a refractive index test. Sapphire is an incredibly hard and durable crystal.

Because it isn't made for that kind of precision, the Mohs scale uses half-numbers for in-between hardness. In terms of absolute hardness, corundum (hardness 9) is 6 times harder than topaz (hardness 8). The Mohs scale is strictly a relative scale, but that's all anyone needs for basic hardness measurement. Whichever mineral scratches the other is harder, if both scratch each other then they are of the same hardness. Here are the ten levels of hardness in minerals on the scale: The Mohs scale was developed by Friedrich Mohs in 1812 and has been a valuable aid in identifying minerals ever since. Sapphires are a 9 on the Mohs hardness scale. The only crystal harder than Corundum (sapphire) is a diamond (cubic crystal structure). HardnessĬorundum is an exceptionally hard crystal structure. Trace mineral content within the crystal gives it color (further details on color explained in each specific sapphire type). Blue Corundum is called Blue Sapphire Pink Corundum is called Pink Sapphire, etc.

Its crystal structure is hexagonal.Ĭorundum (sapphires) comes in all color types. A sapphire (corundum) is an aluminum oxide mineral (Al2O3). The scientific name of a sapphire crystal is called Corundum. If you have general interest in sapphires or if you plan to purchase one this section will give you comprehensive insight into the beautiful world of sapphires! The Sapphire Crystal The more information you understand about these stones the more you will appreciate them.

In this section of our education on sapphires we start with the very basics of the sapphire crystal and its characteristics. Sapphires: Types, Colors, Descriptions, Origins and Details

Raw black sapphire