Dendritic Jasper Identification Guide

What Dendritic Jasper Looks Like

Dendritic jasper is an opaque microcrystalline quartz (jasper) that carries dark, branching, fern- or tree-like inclusions known as dendrites. The body color ranges from cream, tan, and gray to pale yellow or buff, and the dendrites are typically black to reddish-brown manganese and iron oxides.

Key visual cues:

• Body: opaque, earthy or solid colored (cream, tan, gray, beige).
• Luster: dull to waxy; polished pieces look greasy-glassy.
• Transparency: opaque — no light passes through.
• Pattern: branching, planar dendrites that look like landscapes, ferns, or shrubs.

Step-by-Step Field-ID Checklist

1. Confirm opacity. Hold a thin edge to strong light. Jasper stays solid and dark; if light glows through, it's dendritic agate.
2. Examine the dendrites with a loupe. They should branch fractally inside the stone and fade into the body, not float on the surface.
3. Test hardness. It scratches glass and resists a steel knife (Mohs ~7).
4. Check the break. Look for conchoidal fracture with a waxy sheen.
5. Note the background color — jasper bodies are richer and more earthy than the pale, glassy agate host.

Diagnostic Tests

• Mohs hardness: 6.5–7; scratches glass and steel.
• Streak: white to pale (the silica body); dendrites streak dark brown/black.
• Fracture: conchoidal to splintery; no cleavage.
• Density: ~2.6 g/cm³.
• Acid: inert to dilute HCl.
• Magnetism: none.

Common Look-Alikes and How to Tell Them Apart

• Dendritic agate: translucent host that transmits light; dendritic jasper is fully opaque. This is the single most reliable distinction.
• Picture jasper: shows scenic banding and color zoning but lacks branching dendrites; dendritic jasper's pattern is tree-like, not landscape-banded.
• Dendritic limestone/marble: soft (Mohs ~3) and fizzes in acid; jasper is hard and acid-inert.
• Mocha stone (dendritic chalcedony): often translucent and glassier; jasper is more opaque and earthy.
• Painted or dyed imitations: dendrites appear only on the surface and stop abruptly at chips; real dendrites continue into the stone.

Where It Is Found

Dendritic jasper forms where silica-rich solutions cement and replace sediments or fill volcanic cavities, with manganese/iron oxides infiltrating microfractures. It is found worldwide, with notable material from India, Madagascar, the western United States (Oregon, Idaho, Nevada), Brazil, and Australia. Collectors find it as nodules, seams, and waterworn cobbles weathered from volcanic and sedimentary host rock.