Frosted Obsidian Identification Guide

What Frosted Obsidian Looks Like

Frosted obsidian is obsidian (natural volcanic glass) with a dull, matte, frosted exterior produced by weathering, abrasion, or tumbling/etching, while the interior remains glassy. It is amorphous (non-crystalline) silica-rich glass.

• Color: the body is usually black, smoky grey, or brown; the frosted surface looks pale, cloudy, or satin.
• Luster: matte/frosted on the surface, vitreous (glassy) on any fresh chip.
• Transparency: translucent on thin edges, opaque in mass.
• Form: massive glass; no crystals or cleavage; rounded pebbles and nodules often show the frosted skin.

Step-by-Step Field-ID Checklist

1. Chip or check a fresh edge: beneath the frost it should be glossy glass with conchoidal fracture and sharp edges.
2. Hold a thin edge to light: obsidian is translucent (often with a brown or grey tinge).
3. Test hardness against glass (~5–5.5; about the same as window glass).
4. Heft it: glass feels relatively light.
5. Look for the frosted skin as a surface feature only, not throughout.

Key Diagnostic Tests

• Mohs hardness: ~5–5.5. It barely scratches or matches glass; a steel knife may lightly scratch it.
• Streak: white.
• Fracture: conchoidal — smooth shell-like curves with razor edges; no cleavage. Diagnostic of glass.
• Density: ~2.35–2.6 g/cm3, light in the hand.
• No acid reaction, non-magnetic.
• Warmth: glass and obsidian feel slightly warmer than true crystalline minerals.

Common Look-Alikes and How to Tell Them Apart

• Frost agate / frosted chalcedony: harder (7, scratches glass), waxy not glassy interior, and microcrystalline; obsidian is softer (5–5.5) and a true glass. The hardness test separates them.
• Flint: opaque, waxy, hardness 7; obsidian is glassier and softer with a translucent edge.
• Manmade frosted/sea glass: can look identical; sea glass is also glass with conchoidal fracture, but it often shows mold seams, uniform color, or bubbles, and obsidian usually has a smoky translucency and natural inclusions (microlites, snowflake spherulites).
• Apache tears: rounded obsidian nodules; if a frosted pebble is translucent brown-black glass it may itself be a weathered Apache tear.
• Black glass slag: very similar; look for natural surroundings and the lack of a deliberate matte coating; slag often has bubbles and unnatural colors.

The identifier is glassy conchoidal-fracturing interior + hardness ~5–5.5 + translucent edge + light heft + matte surface only on the outside.

Where Frosted Obsidian Is Found

Obsidian forms where silica-rich lava cools too fast to crystallize, at and near rhyolitic volcanic centers. Sources include the western United States (Oregon, California, Nevada, Arizona, New Mexico), Mexico, Iceland, Italy (Lipari), Turkey, and Armenia. Frosting develops on stream-tumbled, wind-abraded, or chemically weathered pieces, or is created by tumbling/etching.