Where is Black Obsidian with Phenocrysts found?

Black Obsidian with Phenocrysts occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.

Where to find Black Obsidian with Phenocrysts

Collecting tips

1. Look for Volcanic Regions. Obsidian is exclusively found in areas of recent (geologically speaking) volcanic activity, particularly where rhyolitic lavas have erupted.
2. Examine Lava Flows and Domes. Obsidian forms on the outer margins of lava flows and domes where cooling is most rapid. Look for glassy, dark rocks.
3. Check for Conchoidal Fracture. A key identifying feature of obsidian is its sharp, curved, shell-like fracture surfaces. The presence of phenocrysts will not alter this characteristic of the glassy matrix.
4. Safety Precautions. Obsidian edges can be extremely sharp, comparable to surgical scalpels. Handle with care, and consider wearing gloves and eye protection when collecting or breaking samples. Avoid inhaling obsidian dust, as it contains crystalline silica (from the phenocrysts) and amorphous silica, which can be a respiratory irritant.

Quick Check

Color:

Black to dark gray/brown with visible lighter or darker mineral inclusions.

Luster:

Vitreous (glassy).

Streak:

White (due to its amorphous nature and high silica content).

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