Red Obsidian Identification Guide

What Red Obsidian Looks Like

Red obsidian is a natural volcanic glass colored red to reddish-brown by tiny dispersed hematite (iron oxide) particles. Pure, evenly red obsidian is uncommon; most "red" obsidian is mottled or streaked, grading toward mahogany obsidian.

• Color: red to red-brown, often streaked or blended with black
• Luster: bright vitreous (glassy)
• Transparency: translucent on thin edges to opaque
• Habit: massive glass, no crystals; flow banding common

Step-by-Step Field ID Checklist

1. Look at a chip or edge for smooth, curved, shell-like conchoidal fracture with sharp edges — the obsidian signature.
2. Backlight a thin edge — obsidian transmits a reddish glow.
3. Check luster — bright glassy shine, not dull or grainy.
4. Test hardness with a steel knife.
5. Watch for flow banding swirling red and black — a natural feature, not seen in glass castings with mold seams.

Key Diagnostic Tests

• Mohs hardness: 5–5.5 — softer than quartz; a steel knife barely marks it, quartz scratches it.
• Fracture: conchoidal, no cleavage — the decisive obsidian test.
• Streak: white to grayish.
• Specific gravity: ~2.35–2.6, low.
• Acid: no reaction.
• Magnetism: not attracted to a hand magnet despite the iron coloring.

Common Look-Alikes and How to Tell Them Apart

• Mahogany obsidian: essentially the same material with brown-and-black banding; "red obsidian" is the redder, more vivid grade. Both share glassy conchoidal fracture.
• Red jasper: harder (7), opaque, with a dull-to-waxy (not bright glassy) luster; jasper is crystalline quartz, not glass.
• Carnelian/red agate: harder (7), waxy luster, translucent; agate is banded.
• Red glass (man-made): look for mold seams, perfectly uniform color, and spherical bubbles; natural obsidian shows irregular flow banding and may contain elongated gas bubbles.

Where It Is Found

Red and mahogany obsidian come from rhyolitic lava flows, notably in the western United States (Oregon, California, Nevada, Arizona) and Mexico.

Collector's Notes and Common Mistakes

The decisive test is hardness plus luster: red obsidian is glass (5–5.5) with a bright vitreous shine and conchoidal fracture, while the most common look-alike, red jasper, is crystalline quartz (7), opaque, and waxy. Try scratching glass — jasper will mark it, obsidian will not. The line between "red obsidian" and mahogany obsidian is gradational; the redder, more uniformly colored material gets the "red" name, while brown-and-black banded pieces are called mahogany, but both are the same volcanic glass. The chief authenticity risk is manufactured red glass: watch for mold seams, perfectly uniform color, and round trapped bubbles, versus the irregular flow banding and elongated bubbles of natural obsidian. Because obsidian is a metastable glass, it slowly devitrifies over geologic time and can be brittle and razor-edged when fresh — handle chips with care and avoid thermal shock. It cabs and tumbles beautifully but scratches easily, so store it apart from harder gems.