amorphous
Obsidian
- Also known as
- volcanic glasssnowflake obsidianrainbow obsidianapache tears
- Crystal system
- amorphous
- Hardness
- 5–6 on the Mohs scale
- Lustre
- vitreous
- Colour
- Black, brown, green, sometimes iridescent
- Where it forms
- When silica-rich lava cools too fast for atoms to arrange into crystals. It is a frozen liquid rather than a solid in the ordinary sense, and given geological time it devitrifies — which is why obsidian older than about twenty million years is essentially unknown.
- Chiefly from
- Lipari, ItalyAnatolia, TurkeyHekla, IcelandOregon and California, United StatesMexico
Why it is that colour
Black comes from suspended magnetite and other iron minerals dispersed through the glass. The sheen and rainbow varieties come from aligned microscopic inclusions or gas bubbles diffracting light.
Safety
Safe to hold, but genuinely sharp. Broken obsidian produces edges a few molecules thick — sharper than a steel scalpel — and it will cut skin very easily. Handle broken pieces as you would broken glass, because that is what they are.
Where it comes from
Widely available and inexpensive. Not a stone with acute sourcing concerns.
Historical use
One of the two great tool stones, alongside flint, and superior to it where available. Obsidian blades take an edge no metal can match, and modern surgical scalpels have been made from it experimentally. Because each volcano’s obsidian has a distinct trace-element signature, archaeologists can source individual artefacts to individual eruptions, which has reconstructed Neolithic trade networks in extraordinary detail.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
Mesoamerican traditions around obsidian are ancient, extensive and specific: the Aztec deity Tezcatlipoca is named for the smoking mirror, and polished obsidian mirrors were used for scrying. That is genuine and documented. The modern reading of obsidian as a protective and grounding stone is New Age and only loosely connected to it.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Sold as this, but not
Worth knowing
Obsidian sourcing is one of the quiet triumphs of archaeological science. Every volcanic source has its own trace-element fingerprint, stable and measurable, so a flake found in a cave can be matched to the specific volcano it came from. That has mapped trade across the Neolithic Mediterranean and the Pacific with a precision nothing else offers — Anatolian obsidian at Jericho, Melian obsidian in mainland Greece before agriculture, Sardinian obsidian across the western Mediterranean.
The scrying tradition is real. John Dee's obsidian mirror, now in the British Museum, is Aztec, and analysis published in 2021 confirmed the source as Mexican. An Elizabethan magician was looking into Mesoamerican volcanic glass.
Identity checked against IMA-CNMNC master list, June 2025.