Have you ever found yourself in a museum's gallery of human origins, staring at a glass case full of rocks labeled "stone tools," muttering under your breath, "How do they know it's not just any ...

Its lattice-free insides may be unpredictable, but obsidian breaks in a very reliable “conchoidal fracture” pattern.

Many prehistoric people prized obsidian — volcanic glass — for its combination of beauty and utility. Its color can range from black to mahogany to red, and its conchoidal fracture means tools ...

A stone like obsidian, which is volcanic glass, is the poster child for conchoidal fracture.

Jennifer Yeoman and Hector Lomack, a couple in Edmonton, Alberta, stumbled upon a significant find while landscaping their front yard: a 4.6-pound obsidian core, rare in a region without volcanic ...

The blackness is intensified when its shiny surface is broken, and it breaks easily into sharp chips due to a glass condition called conchoidal fracture … and obsidian is a type of glass that ...

Mr. Schumacher states that obsidian is not the only stone used, but chert, chalcedony, jasper, agate, and similar stones of conchoidal fracture.

It’s brittle and has a conchoidal fracture. This means that when you break it, the pieces resemble a seashell. It’s also incredibly dense thanks to the bismuth it contains.

A very conspicuous and important formation consists of green rock, easily breaking up into small angular fragments, commonly with conchoidal fracture.

When broken, conchoidal fractures occur, meaning it breaks apart into curved surfaces with incredibly sharp edges — sharper even than contemporary steel surgical scalpels.

Obsidian hand ax made by John Murray, showcasing examples of conchoidal fracture produced while making flakes to shape it. John K. Murray ...