Aurora Obsidian Identification Guide

What Aurora Obsidian Looks Like

Aurora obsidian is a trade name for rainbow/sheen obsidian — natural volcanic glass that shows a multicolored iridescent sheen (greens, golds, purples, blues, pinks) when light catches it at the right angle. The body is black and opaque in ordinary light; the colors are a surface-aligned sheen, not body color. Like all obsidian it has a brilliant glassy (vitreous) luster and breaks with a smooth conchoidal fracture. The sheen comes from microscopic aligned inclusions (nanoparticle layers, commonly of magnetite or hedenbergite) that diffract light.

Step-by-Step Field ID Checklist

1. Confirm it is obsidian — black, glassy, no visible crystals, conchoidal fracture with razor-sharp edges.
2. Tilt it under a strong directional light — rotate the piece to bring out bands or sheets of rainbow color that move as you turn it.
3. Distinguish sheen from body color — the iridescence appears and disappears with angle; in flat light the stone looks plain black.
4. Feel the weight and warmth — glass feels slightly warm and light compared with similar-looking minerals; not as cold as true crystal.
5. Check for flow banding or bubbles that betray a glassy, volcanic origin.

Key Diagnostic Tests

• Hardness: 5–5.5; it will scratch glass marginally and be scratched by quartz and steel files.
• Fracture: Conchoidal (smooth, curved, shell-like) with very sharp edges — characteristic of glass.
• Luster: Bright vitreous/glassy.
• Streak: White to pale gray.
• Transparency: Opaque to translucent on thin edges, often warm brown when backlit.
• No cleavage: Glass has no crystal cleavage; only conchoidal fracture.
• Specific gravity: ~2.35–2.6, relatively light.

Common Look-Alikes and How to Tell Them Apart

• Manufactured/slag glass and "goldstone": Man-made glass can mimic sheen, but goldstone shows tiny sparkling copper flecks (aventurescence), not a diffuse rainbow sheen, and may have a too-perfect color. Obsidian's sheen is subtle and directional with natural flow features.
• Rainbow/fire obsidian (other trade names): Essentially the same material; "aurora," "rainbow," and "fire" obsidian differ mainly in sheen intensity and marketing.
• Labradorite/spectrolite: A feldspar with similar flashy color (labradorescence) but it is crystalline, harder (6–6.5), shows cleavage planes, and is not glassy with conchoidal fracture.
• Black onyx / black agate: These are chalcedony, harder (~7), waxy not glassy, and lack the rainbow sheen.
• Apache tears: Rounded translucent obsidian nodules, usually without strong rainbow sheen.

Where Aurora Obsidian Is Found

Obsidian forms from rapidly cooled, high-silica (rhyolitic) lava, so it occurs around young volcanic centers. Sheen-producing obsidian is recovered from deposits in Mexico (a major source of rainbow/sheen and "fire" obsidian), the western United States (Oregon, Arizona, California, Nevada), and other volcanic regions. The specific iridescence depends on the nanoparticle layering within a given flow.