Paintbrush Jasper Identification Guide

What Paintbrush Jasper Looks Like

Paintbrush Jasper is an opaque, fine-grained silica rock (jasper) whose iron and manganese coloration is arranged in sweeping, brushstroke-like streaks and swirls, giving the appearance of painted strokes across the stone. Typical palettes mix red, ochre, brown, cream, gray, and black. Because it is jasper, it is fully opaque and stony, polishing to a smooth glassy shine while rough surfaces look waxy to dull.

• Color: reds, browns, ochres, creams, grays, black in flowing streaks
• Transparency: opaque
• Luster: dull/waxy rough; vitreous polished
• Habit: massive jasper seams and nodules

Step-by-Step Field ID Checklist

1. Confirm opacity. No light passes through - this separates it from paintbrush agate.
2. Read the strokes. Look for directional, sweeping color streaks, not concentric bands.
3. Hardness test. Scratches glass; resists a steel knife (Mohs ~7).
4. Examine fracture. Conchoidal, grainless, no cleavage.
5. Acid test. No fizz with dilute HCl.
6. Check uniform density typical of silica (~2.6 g/cm3).

Key Diagnostic Tests

• Mohs hardness: 6.5-7.
• Streak: white.
• Fracture: conchoidal; no cleavage.
• Acid: inert.
• Density: ~2.6 g/cm3.

Common Look-Alikes and How to Tell Them Apart

• Paintbrush Agate: translucent with 3D internal plumes; the jasper is opaque with surface-plane color streaks.
• Picture/Polychrome Jasper: similar opaque scenic jasper; paintbrush emphasizes linear brush-like strokes rather than landscape scenes.
• Rhyolite: softer, more granular and porous; will not polish to a glassy jasper finish.
• Dyed jasper or marble: dye pools in cracks and color looks artificially uniform; carbonate marble also fizzes in acid and is much softer.
• Petrified wood: shows preserved wood grain and rings.

Where It Is Found

Paintbrush-patterned jaspers come from volcanic and silica-replacement deposits in the western United States (Oregon, Nevada, Idaho, Arizona) and similar settings worldwide such as Madagascar, where iron- and manganese-bearing fluids streaked silica during deposition. It is collected as desert float and from in-place seams.