Geological Information

Geological Information of Obsidian Family

• Naturally occurring volcanic glass formed as an extrusive igneous rock which cools too quick to create crystals bigger than micro.

General Identification

• Type: Rock
• Class: n/a - high silica content
• Member of Group: Chrysoberyl
• Mohs Hardness: 5 - 6
• Crystal Habit: Amorphous
• Lustre / Diaphaneity: Translucent, Vitreous, Glassy
• Colour: black, bluish, mahogany, golden, peacock, etc. - the colors due largely to refraction by microscopic bubbles (and microscopic mineral inclusions such as magnetite in "Rainbow Obsidian").
• Snowflake obsidian, formed through the inclusion of cristobalite crystals.
• Mahogany obsidian is a combination of red brown and black colours due to magnetite or haematite oxidising within the Obsidian.
• Apache tears are small rounded obsidian nuggets often embedded within a grayish-white perlite matrix.

Obsidian in green, blue, aquamarine/aqua, peach, purple, yellow

• The real green obsidian from Middle East ran out some years ago.
• What is sold on market is actually coloured man-made glass, often made in Indonesia.
  • some vendors sell as "we are not sure if real" if you question them but I have found no positive proof that there is natural supply over the ten year.
  • Helenite obsidian is at least melted down ask from Mt St Helens, USA.
    • The silica, aluminium, iron, and trace amounts of chromium and copper present in the rocks and ash in the area, combined with the heat of the torches, transformed the volcanic particles into a compound
• Appearance: Transparent
• Aquamarine obsidian is now being sold as just aquamarine.

Special Notes

• Obsidian is hard and brittle and therefore fractures with very sharp edges.
  • In the past it was used to manufacture cutting, piercing tools and arrowheads.
• Obsidian is also used for ornamental purposes and as jewellery.
  • It presents a different appearance depending on how it is cut: in one direction it is jet black, while in another it is glistening gray.
• The first known archaeological evidence of usage was 700,000 BCE.
• Rainbow usually needs careful cutting to bring out the multi coloured layers.
• Variations where the colours are many but the layering is not obvious may be called velvet obsidian.
• Read more geological information.