Jasper… but more precisely chert

In lapidary circles “jasper” is a friendly umbrella for colorful, opaque microcrystalline quartz. Petrographically, Mookaite is a silicified radiolarite/chert—a dense, cryptocrystalline mosaic of quartz (with moganite) formed from silica‑rich marine sediments.

Where the name comes from

It’s named for Mooka Creek in Western Australia’s Kennedy Ranges. You’ll sometimes see “Mookite,” but “Mookaite” has stuck. Many locals note that “Mooka” is associated with nearby springs—fitting for a stone born from ancient seas.

Radiolarian rain

In Cretaceous seas, microscopic plankton called radiolarians built shells of silica. When they died, their tests settled into siliceous ooze on the seafloor—think snow globe, but with glassy micro‑skeletons.

Burial & diagenesis

Buried under more sediment, the ooze compacted and re‑organized into chert. Silica dissolved and re‑precipitated, sealing grains into a tight cryptocrystalline fabric. Iron in the pore waters painted the stone from cream to burgundy.

Silicification & healing

Later fluids moved through, silicifying remaining pores and healing micro‑cracks with chalcedony. Local brecciation (natural breakage) and re‑cementation created the mosaics and ribbons that make Mookaite so graphic.

Palette (classic Mookaite)

• Cream / ivory — chalcedony‑rich zones.
• Mustard / saffron — goethite/limonite tints.
• Deep red / burgundy — hematite iron oxide.
• Plum / mulberry — mixed Fe states & subtle organics.
• Ochre / tan — oxidized margins and veins.
• Frosty white — silica “healed” fractures.

Most pieces are opaque with a glassy polish; thin edges in cream zones can be faintly translucent under strong light.

Pattern words you’ll see

• Color‑blocking — large swaths of contrasting hues.
• Ribboning — parallel bands from layered deposition.
• Breccia mosaic — angular fragments re‑cemented by silica.
• Feathering — soft, brushy transitions where iron diffused.
• Veinlets — hairline chalcedony/quartz filling tiny cracks.

Photo tip: Side‑light at ~30° enhances contrast between matte iron‑rich patches and glassier chalcedony heals—no filter needed.

Sugar‑fine mosaic

At 10×, most surfaces show a tight, sugary micro‑grain with no discrete crystals. Polished faces look glassy; matte areas often coincide with iron‑rich patches.

Veins & heals

Look for hairline chalcedony/quartz veinlets crossing color blocks, sometimes with slightly translucent, frosty margins—evidence of post‑depositional silica “glue.”

Breccia clues

Angular color islands with sharp boundaries and a different orientation indicate brecciation and recementation—one reason cabs can look like graphic art.

Polychrome jasper (Madagascar)

Also bold and earthy, but tends toward pastel gradients with more flowing, orbicular forms. Mookaite skews mustard–burgundy and often shows sharp color blocks.

Picasso jasper

Grey‑tan palette with black linear veining (manganese) rather than saturated reds/yellows. Patterns look penciled rather than painted.

Porcelain jasper (Sierra Madre)

Similar fine texture, but colors run lilac‑cream‑grey with delicate “porcelain” marbling, not the ochre‑maroon punch of Mookaite.

Bumblebee “jasper” (not a jasper)

Vivid yellows/oranges/black from sulfur/arsenate in carbonate rock—very different chemistry and often banded like caution tape.

Rhyolite (rainforest jasper)

Volcanic rock with orbicules and spherulites; more glassy/porphyritic textures. Mookaite is micro‑quartz throughout with uniform hardness.

Quick checklist

• Australian provenance (Mooka Creek area) is a strong clue.
• Mustard–burgundy–cream blocks with high, glassy polish.
• Micro‑quartz texture; no large crystals, no true banded agate.

Mooka Creek, Kennedy Ranges (WA)

The type and classic area for Mookaite. Material occurs within silicified Cretaceous sediments of the region—often in float and shallow pits along drainage lines and low rises.

Sense of exclusivity

While colorful cherts occur worldwide, “Mookaite” is closely tied to this Western Australian source and its distinctive palette. Similar looks elsewhere are usually sold under other jasper names.

Everyday handling

• Hard, durable (~7 Mohs) and non‑porous—good for daily wear.
• Edge chips are possible if struck; treat cabs like glassy quartz.

Cleaning

• Lukewarm water + mild soap + soft cloth/brush; rinse and dry.
• Avoid harsh acids/bleach (can haze iron‑rich skins).

Lapidary

• Cuts and polishes beautifully with diamond or SiC → cerium/oxide finish.
• Watch for micro‑fractures along healed veinlets; use light pressure and support the cab’s edges.
• For drama, orient slabs to let color blocks traverse the dome.