What is Obsidian?


Obsidian is a naturally occurring volcanic glass formed when felsic lava cools rapidly without crystal growth. Unlike many other gemstones, which are formed under pressure over long periods, Obsidian’s formation is almost instantaneous, capturing a unique snapshot of its environment at the time of its creation. This rapid formation gives it a smooth, glass-like texture that is often used for sharp tools and ornamental objects. Obsidian is found in various locations worldwide, including the United States, Mexico, and Japan. Its unique formation and properties have made it a subject of fascination in both scientific and metaphysical circles.

Obsidian is a striking volcanic glass known for its smooth texture and deep black color, although it can also appear in shades of brown, tan, or green. Its glass-like appearance and unique formation process make it a popular choice for both ornamental and practical uses. The stone has been used for millennia for tools, weapons, and jewelry, and it continues to be a subject of fascination for geologists and spiritual practitioners alike.

Gemstone Properties

Chemical ClassificationInorganic - Silicate (Volcanic glass)
ColorTypically black, but can also be found in brown, or green. Some varieties, like snowflake obsidian, have patterned inclusions.
OccurrenceUSA, Mexico, Japan.
FormationObsidian is formed from rapidly cooling lava, which doesn't allow crystals to form.
DiaphaneityTranslucent to opaque
Mohs Hardness5 to 5.5.
Specific GravityApproximately 2.4.
Diagnostic PropertiesConchoidal fracture, vitreous luster, often black.
Chemical CompositionMostly SiO2 (with various impurities)
PleochroismNot exhibited in obsidian.
Crystal SystemAmorphous (volcanic glass)
Optical PropertiesIsotropic (due to its amorphous nature)
Refractive Index1.450 - 1.550
BirefringenceNone (isotropic due to amorphous nature)
2V angleNot applicable (amorphous)
DispersionNot typically relevant for obsidian.