Onyx Vs. Pearl

Onyx is a very popular gemstone composed of silicon dioxide.^[1] Pearl is also a very popular gemstone and its chemical composition is calcium carbonate.^[2]

Quick Facts on Differences of Onyx and Pearl

For a quick recap of the differences onyx and pearl:

• In terms of crystallography, onyx can be hexagonal or trigonal while pearl is orthorhombic.
• For chemical formulas, onyx is SiO2 while pearl is CaCO3.
• In terms of luster, onyx can be vitreous or waxy while pearl can be dull or pearly.
• Onyx can be commonly black while pearl can be commonly cream or white.
• Onyx's rarity is less rare than pearl.
• Onyx's hardness is higher than pearl - onyx is 7 and pearl ranges from 2.5 to 4.5 on the Moh's scale.

Quick Facts on Similarities of Onyx and Pearl

The similarities of onyx and pearl include:

• Onyx and pearl both can be opaque or translucent.
• Onyx and pearl both streak white.
• Onyx's specific gravity overlaps with pearl - onyx is 2.651 and pearl ranges from 2.6 to 2.72.

Summary of Onyx

Onyx is a mineral that belongs to the chalcedony family, which is a type of quartz that is formed by the deposition of silica in the cavities of rocks. It is a cryptocrystalline mineral, which means that its crystals are too small to be seen with the naked eye. Onyx is typically black, but it can also be found in other colors such as white, gray, brown, and green. It has a waxy luster and a smooth, polished surface.

Summary of Pearl

Pearl is a mineral that is formed within the shells of certain mollusks, particularly oysters and mussels. It is a hard, round, lustrous object that is highly prized for its beauty and rarity. Pearls are formed when a foreign object, such as a grain of sand or a piece of shell, enters the mollusk and irritates its soft tissue. The mollusk then secretes a substance called nacre around the irritant, layer upon layer, until a pearl is formed.

Table Comparison of Onyx vs Pearl