Obsidian forms as lava, ... which chemists bathe in molten salts to forcibly strengthen its chemical structure, ... those little rocks are used as meditation stones.

The stone at Obsidian Cliff has few inclusions, which means it lacks the presence of mineral crystals that can weaken the stone’s structure, and that contributes to the high quality of the ...

Mayan child sacrifices in Guatemala were buried with 'supernatural' jet black volcanic stones 4,000 years ago. Scientists found obsidian while excavating the ancient Mayan city of Ceibal ...