Mineraloid
Obsidian
Obsidiyen
Nature’s volcanic glass — the shiny black stone that gave the Stone Age its sharpest blades.
Also known as: Volcanic glass
- Ornamental
- Important in Türkiye
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In short
Obsidian is a natural glass that forms when thick, silica-rich lava hardens before it has a chance to form crystals. When it breaks, it makes curved surfaces and extremely sharp edges, just like glass. Stone Age people used it to make knives, arrowheads and other cutting tools.
How does it form?
Obsidian forms when very silica-rich lava, mostly of rhyolitic composition, solidifies at the surface. Such lava is extremely thick (viscous), so its atoms cannot move easily enough to arrange themselves into crystals. When it cools under these conditions it becomes glass instead. That is why obsidian is not a mineral but a mineraloid, a solid without an ordered atomic structure.
Glass is not stable over geological time: obsidian very slowly crystallises (devitrifies). As a result, obsidian is found mostly in geologically young volcanic areas.
What is it used for?
In the Stone Age obsidian was one of the most valued raw materials for knives, arrowheads and scrapers because of its sharp edges. Each obsidian source has its own chemical “fingerprint”, so archaeologists can tell which volcano a tool came from and trace prehistoric trade routes. Today obsidian is used mainly as an ornamental stone in jewellery and small decorative objects.
Obsidian in Türkiye
Anatolia is home to many of the most important obsidian sources of the prehistoric Near East. Göllüdağ and Nenezi Dağ in Cappadocia were the main obsidian sources of the Neolithic settlement of Çatalhöyük in Konya. In the east, obsidian flows also occur in the caldera of Nemrut volcano in Bitlis.
How to recognise it
- 1
It is glassy and shiny, usually black; thin edges held up to the light look brownish or greyish and translucent.
- 2
It breaks with curved, shell-like surfaces and razor-sharp edges.
- 3
No crystals are visible; sometimes it has white “snowflakes”, flow bands, or a golden or rainbow sheen.
- 4
Its hardness is close to that of window glass (about 5–5.5); a steel file can scratch it.
Fakes and imitations
What shops usually don’t tell you:
- Transparent “obsidian” in vivid blue, green, red or yellow is almost always man-made glass; natural obsidian is not that bright and saturated.
- Black bottle glass can look like obsidian, but round air bubbles, mould marks or a perfectly uniform look give it away.
- Small rounded pieces sold as “Apache tears” are genuine obsidian; the name is a trade name, not a different stone.
Safety
Freshly broken obsidian edges can be sharper than a razor blade and easily cause deep cuts. Wear safety glasses and gloves when breaking or knapping it, and do not pick up small glass splinters with bare hands.
Did you know?
Polished obsidian discs about 8,000 years old found at Çatalhöyük are counted among the oldest known mirrors.
An obsidian blade can have a far finer edge than a steel scalpel, which is why some surgeons use obsidian blades for special operations.
Where is it found?
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- Nemrut Caldera, Tatvan, Bitlis, Türkiye · Major depositObsidian flows and blocks occur in the caldera of Nemrut volcano west of Lake Van; an archaeologically important obsidian source.
- Göllüdağ, Niğde, Türkiye · Historic sourceTogether with nearby Nenezi Dağ, this Cappadocian volcanic complex was a main source of the obsidian found at Çatalhöyük; many prehistoric obsidian workshops lie around it.
- Lipari, Aeolian Islands, Italy · Historic sourceOne of the most important obsidian sources of the Neolithic Mediterranean.
- Obsidian Cliff, Yellowstone, Wyoming, USA · Historic sourceFirst quarried for toolmaking more than 11,000 years ago; its obsidian has been found thousands of kilometres to the east, in Hopewell burial sites of the Ohio River Valley. A National Historic Landmark since 1996.
Locations are approximate to protect sites. Red dots mark places in Türkiye. Open in the big map →
Sources
- Obsidian · Encyclopaedia Britannica
- Obsidian Cliff · U.S. National Park Service (Yellowstone National Park)
- A new programme of obsidian characterization at Çatalhöyük, Turkey (Carter, Poupeau, Bressy & Pearce), Journal of Archaeological Science 33(7) · Elsevier, 2006
External links
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