Cloudy Obsidian Identification Guide

What Cloudy Obsidian Looks Like

Cloudy obsidian is natural volcanic glass that is partly translucent with misty, smoky, or veil-like internal clouds rather than being uniformly black and opaque. The haze comes from microscopic gas bubbles, water content, and incipient devitrification (the very early stages of crystallization within the glass). Color is typically smoky gray to gray-brown, sometimes with darker swirls. Luster is glassy, and fresh breaks show the smooth curved conchoidal fracture typical of all obsidian.

Step-by-Step Field ID Checklist

1. Backlight it. Look for partial translucency with internal smoky clouds and swirls.
2. Inspect the fracture. A clean curved (shell-like) break with sharp edges confirms glass.
3. Check for crystals. There should be none — obsidian is amorphous; any crystals are tiny clouds, not faces.
4. Test hardness. Scratches glass but is scratched by quartz (Mohs ~5–5.5).
5. Feel temperature and weight. Glass feels warmer and lighter than crystalline quartz.
6. Look for swirl banding. Flow lines and bubble trains indicate volcanic glass.

Key Diagnostic Tests

• Hardness: 5–5.5. Quartz (7) scratches it; a steel knife barely marks it.
• Streak: White.
• Fracture: Conchoidal, no cleavage — decisive versus crystalline look-alikes.
• Density: ~2.35–2.6 g/cm³.
• No acid reaction, non-magnetic.
• Texture: Amorphous glass with internal haze, bubbles, and flow swirls.

Common Look-Alikes and How to Tell Them Apart

• Snowflake obsidian: Has distinct white/gray spherulites (radiating cristobalite "snowflakes") with crisp edges. Cloudy obsidian's haze is diffuse and lacks defined snowflake spheres.
• Smoky/milky quartz: Crystalline, hardness 7, may show hexagonal faces and no conchoidal-only fracture; feels cold. Cloudy obsidian is glass, hardness 5.5.
• Clear obsidian: More transparent with fewer clouds; same material, differing only in clarity.
• Chalcedony: Harder (6.5–7), waxy luster, and translucent without obsidian's glassy swirl banding.
• Glass slag: Often too uniformly bubbly or oddly colored; locality and natural swirl help confirm true obsidian.

Where It Is Found

Cloudy obsidian forms in high-silica rhyolitic lava flows that cooled fast but trapped water and bubbles. Localities include Glass Buttes (Oregon), California, Nevada, Idaho, Mexico, and Armenia. Look on eroding obsidian flows, talus slopes, and stream gravels where rough nodules accumulate.