Obsidian
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.
| Chemical Classification | Inorganic - Silicate (Volcanic glass) |
| Color | Typically black, but can also be found in brown, or green. Some varieties, like snowflake obsidian, have patterned inclusions. |
| Streak | White |
| Luster | Vitreous. |
| Transparency | Opaque. |
| Occurrence | USA, Mexico, Japan. |
| Formation | Obsidian is formed from rapidly cooling lava, which doesn't allow crystals to form. |
| Diaphaneity | Translucent to opaque |
| Cleavage | Conchoidal |
| Mohs Hardness | 5 to 5.5. |
| Specific Gravity | Approximately 2.4. |
| Diagnostic Properties | Conchoidal fracture, vitreous luster, often black. |
| Chemical Composition | Mostly SiO2 (with various impurities) |
| Pleochroism | Not exhibited in obsidian. |
| Crystal System | Amorphous (volcanic glass) |
| Optical Properties | Isotropic (due to its amorphous nature) |
| Refractive Index | 1.450 - 1.550 |
| Birefringence | None (isotropic due to amorphous nature) |
| 2V angle | Not applicable (amorphous) |
| Dispersion | Not typically relevant for obsidian. |