OBSIDIAN

Obsidian is a naturally occurring volcanic glass that forms when lava erupts from a volcano and cools quickly, resulting in minimal crystal development. Classified as an igneous rock, it originates from felsic lava, which contains a high concentration of lighter elements like silicon, oxygen, aluminum, sodium, and potassium. Typically found at the edges of rhyolitic lava flows, known as obsidian flows, this material has a significant silica content that contributes to its high viscosity. This viscosity restricts atomic diffusion within the lava, preventing the initial nucleation phase necessary for mineral crystal formation, leading to the creation of natural glass through rapid cooling. 

Characterized by its hardness, brittleness, and amorphous structure, obsidian fractures to produce sharp edges. Historically, it was utilized for crafting cutting and piercing tools, and it has also been explored for use in surgical scalpel blades.