“Jasper” or rhyolite?

In strict terms, jasper is microcrystalline quartz (chalcedony) throughout. Leopardite’s matrix is typically rhyolite—fine‑grained quartz + feldspar—so the “jasper” tag is a long‑standing trade habit. Many collectors still file it under “leopard skin jasper,” but petrographically, think orbicular rhyolite.

Why “leopard”?

The circular to rosette‑like patches (often with a pale core and a darker ring) mirror animal coat patterns. Iron and manganese oxides emphasize the rims, while silica infill lightens the centers—nature’s own spot filter.

Stage 1 — Glass to crystals

When silica‑rich lava cools quickly, it may first solidify as volcanic glass. Over time, that glass devitrifies: tiny crystals of quartz and feldspar grow outward from seed points, making round spherulites—the “spots.”

Stage 2 — Coloring the rings

Fluids moving through the rock supply iron and manganese. These oxides concentrate around spherulite edges, painting dark halos that heighten the leopard effect.

Stage 3 — Fill the gaps

Micro‑cavities and fractures can later fill with silica, light carbonate, or clay minerals. These infills make pale centers and smooth transitions between rosettes—like a watercolor wash between spots.

Palette

• Cream / buff — common matrix color.
• Pink‑salmon — warm cores of orbs.
• Orange‑ochre — iron‑rich zones.
• Charcoal / brown‑black rims — manganese/iron oxides.
• Grey — silica‑rich patches and fine groundmass.

Pattern vocabulary

• Rosettes: pale cores with dark rings.
• Ocelli (“little eyes”): multiple rings or bull’s‑eyes.
• Clusters: overlapping orbs that form “rosette fields.”
• Flow ghosts: faint streaking that hints at the original lava flow.

Photo tip: Side‑light at ~30° brings out rim contrast; a white bounce card opposite the light evens the cream tones.

Spherulites

At 10×, many spots reveal a radial micro‑fibrous texture—quartz and feldspar blades growing outwards. Some centers show tiny cavities later filled with silica.

Oxide rims

Dark rings are often manganese/iron oxides along the spherulite margins. Under magnification, they look granular and discontinuous rather than painted.

Flow & fractures

Subtle alignment of microlites may mark ancient lava flow directions. Hairline fractures can host thin quartz or calcite veinlets, sometimes bright white.

Ocean jasper (Madagascar)

Also orbicular, but it’s chalcedony/agate (true jasper variety). Often shows banded agate rims and drusy pockets with quartz crystals—textures are more “agate‑like” than feldspathic.

Poppy jasper

Red/orange orbicules in a jasper matrix; colors are richer ruby to brick. Under a loupe, poppy jasper looks microcrystalline throughout (no feldspar grains).

Mookaite & other radiolarian cherts

Bold reds/yellows but generally lack circular rosettes; the texture is sugary microquartz, not spherulitic devitrification.

Dalmatian “jasper”

Black spots on beige are not orbicular rhyolite—this stone is an igneous rock with dark amphibole/pyroxene spots; no concentric halos.

Dyed/printed composites

Some synthetics mimic spots with uniform color and sharp, “inked” edges. Look for dye pooling in pores and perfectly repeatable patterns—nature rarely copy‑pastes.

Quick checklist

• Round spots with natural, uneven halos.
• Feldspar/quartz groundmass (not banded chalcedony).
• Granular oxide rims under magnification, not smooth dye.

Where it’s found

Leopard‑patterned orbicular rhyolites are most commonly traded from Mexico and Peru. Similar spotted rhyolites occur wherever silica‑rich volcanic flows devitrify—often in ancient volcanic provinces and their surrounding tuffs.

Geologic context

Look for welded tuffs and rhyolite flows that cooled quickly, then slowly reorganized into spherulites. Later groundwater circulation contributes the oxide outlines that make the pattern pop.

Everyday handling

• Hardness around 6–7 handles daily contact, but edges can chip on impact.
• Wipe with a soft cloth to keep the polish bright and the contrast crisp.

Cleaning

• Lukewarm water + mild soap + soft brush; rinse and dry.
• Avoid bleach, strong acids/alkalis, and prolonged soaking in harsh cleaners.
• If you suspect dye on a porous piece, a cotton swab with isopropyl alcohol on an inconspicuous edge can reveal bleeding—skip if you’re unsure.

Storage & display

• Store separately from very hard silicates (e.g., corundum) to protect the polish.
• Side‑lighting around 30° emphasizes the ring contrast for photos.