Ruby

Hardness: 9 (Mohs scale), Color: Typically red, but can be pink, purple, orange, brown, or black depending on trace elements. Luster: Vitreous to adamantine. Crystal Structure: Hexagonal (trigonal) crystal system. Cleavage: None. Specific Gravity: 3.95-4.05.

Rubies form in metamorphic rocks, such as marble or basalt, or in igneous rocks rich in aluminum and low in silica. They crystallize from high-temperature and high-pressure conditions deep within the Earth's crust. Geological Age: Varies widely, from Precambrian to Cenozoic, depending on the specific deposit.

Primarily used as a precious gemstone in jewelry (rings, necklaces, earrings). Also used in lasers (especially early ruby lasers) and for various industrial applications requiring extreme hardness and durability, such as watch bearings and precision instruments.

Rubies are one of the 'big four' gemstones, alongside diamonds, sapphires, and emeralds. Their red color comes from chromium. The most valuable rubies are often referred to as 'pigeon's blood' red. Large, high-quality rubies are rarer than comparable diamonds.

In the field, rubies are often found as hexagonal prismatic crystals, sometimes within host rock or as alluvial pebbles in riverbeds. Look for their distinct red color and high hardness. Common locations include Myanmar (Burma), Thailand, Sri Lanka, Afghanistan, Australia, Cambodia, India, Madagascar, Mozambique, Pakistan, Tanzania, and the USA (North Carolina, Montana). For collectors, identifying natural rubies requires an understanding of their typical crystal habits, specific gravity, and pleochroism (color change with viewing angle). Synthetic rubies are common and can be distinguished by internal inclusions and growth patterns.