Lilac Obsidian Identification Guide

What Lilac Obsidian Looks Like

Lilac obsidian is a variety of obsidian — natural volcanic glass — showing a soft purple, lavender or lilac tint, sometimes as a sheen or as cloudy zones within darker glass. Like all obsidian it is amorphous (non-crystalline), having formed when silica-rich lava cooled too fast to crystallize. The purple coloration comes from fine inclusions, light scattering, and trace elements; many "lilac" pieces are translucent grey glass with a violet cast rather than uniformly deep purple.

• Color: lavender to lilac-grey, sometimes with smoky or banded zones
• Luster: bright vitreous (glassy)
• Transparency: translucent to nearly opaque
• Form: massive glassy chunks; no crystal faces
• Fracture surfaces: smooth, curved, shell-like (conchoidal)

Step-by-Step Field-ID Checklist

1. Look for conchoidal fracture. Obsidian breaks in smooth, curved, scalloped surfaces with razor-sharp edges — the single most telling feature.
2. Confirm a glassy luster and the absence of any crystals, grains, or cleavage planes.
3. Hold it to light. Most lilac obsidian is at least translucent at thin edges, glowing a soft purple.
4. Check for gas bubbles or flow banding under magnification — round bubbles and swirling bands confirm a glass of volcanic origin.
5. Test hardness lightly on a less important spot; obsidian scratches glass but is not extremely hard.

Key Diagnostic Tests

• Mohs hardness: about 5–5.5 — will scratch a steel knife only marginally and can be scratched by quartz.
• Streak: white.
• Cleavage: none; fracture is conchoidal.
• Specific gravity: roughly 2.35–2.6, light to moderate.
• No magnetism; no acid reaction.
• Warmth/feel: glass feels cool but warms in the hand faster than denser stone; manufactured glass feels similar, so this is not decisive.

Common Look-Alikes and How to Tell Them Apart

• Manufactured (slag/art) glass: the biggest concern, since "lilac obsidian" on the market is sometimes man-made glass. Natural obsidian usually shows subtle flow banding, irregular bubbles, and slight color unevenness; factory glass often has perfectly uniform color and very regular bubble trains. Provenance and price are practical clues.
• Amethyst / purple quartz: harder (Mohs 7), often shows crystal faces or a crystalline (not glassy) interior, and is more transparent with sharper color.
• Fluorite: purple but much softer (Mohs 4) with perfect octahedral cleavage — obsidian has no cleavage.
• Purple chalcedony/agate: waxy luster and microcrystalline; harder (7) and does not show large glassy conchoidal surfaces.
• Other obsidians (rainbow, purple sheen): related glass; lilac refers to the body tint rather than an iridescent sheen, though some overlap exists.

Where It Is Typically Found

Obsidian forms at the margins of rhyolitic lava flows and volcanic domes in regions of relatively recent silicic volcanism — the western United States (Oregon, California, Idaho, Arizona), Mexico, and other volcanic belts. Distinctly lilac-toned material is uncommon; much of what is sold under that name is enhanced or manufactured, so be cautious and buy from reputable sources.