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Mookaite: The Radiolarite Jasper of the Kennedy Range

By Digital Towns Crystals ยท Last reviewed October 8, 2026

Short answer: mookaite is a hard, fine-grained silica rock from Mooka Creek on the western side of the Kennedy Range in Western Australia. Geologically it is silicified radiolarite: a Cretaceous sea-floor ooze of microscopic silica shells, later cemented and then stained by groundwater iron into mauve, red, maroon, yellow, cream and brown. It is sold as "mookaite jasper". Strictly, the name belongs to that Australian deposit, which makes origin labels the main thing to read carefully.

What is mookaite made of?

Mookaite starts as plankton. Radiolarians are single-celled marine organisms that build glassy skeletons of silica, and according to the University of California Museum of Paleontology they range from 30 microns to 2 mm across, are mostly planktonic and go back to the early Cambrian. When they die in large numbers, their skeletons settle to the sea floor as a siliceous ooze.

Geology.com describes radiolarites as cherts formed mainly from the thin siliceous shells of radiolarians, and explains how they harden: the shell debris partly dissolves and is redeposited as a silica cement. That gives a rock made almost entirely of microcrystalline silica, the same basic material as chert, flint and jasper.

The peer-reviewed description comes from gemologists Susan and Vernon Stocklmayer, writing in the Journal of Gems & Gemmology (2010). They describe mookaite petrographically as silicified radiolarite of the Windalia Radiolarite formation, part of the sedimentary sequence of the large Carnarvon Basin. After silicification turned the rock into porcellanite, iron staining produced its yellow, red, purple and brown patterns. They add the property that matters most to a cutter: the porcellanite is fine-grained and hard with no directional weaknesses, and it takes an excellent polish.

Property Mookaite
Rock type Silicified radiolarite (porcellanite, chert)
Main component Microcrystalline silica, SiO2
Formation Windalia Radiolarite, Carnarvon Basin
Age Late Aptian, Early Cretaceous
Hardness Close to jasper, about 6.5 to 7, softer in porous zones
Luster when polished Vitreous to waxy
Colors Mauve, plum, red, maroon, mustard yellow, cream, white, brown

The hardness row borrows the figure Minerals.net gives for jasper, 6.5 to 7, with a specific gravity of 2.63 to 2.65. Mookaite is not a mineral species, so no database assigns it its own fixed values; dense, well-silicified pieces behave like jasper, and chalky or porous patches are softer.

When and where did mookaite form?

The Windalia Radiolarite belongs to the Early Cretaceous. A Geoscience Australia paper summarized on data.gov.au places it in the late Aptian, above the Muderong Shale in the Carnarvon Basin, and describes that period as part of the progressive submergence of vast areas of the Australian continent during the Early Cretaceous. Shallow seas spread inland, and radiolarian ooze accumulated on their floors.

Today those sea beds are dry country. The Kennedy Range, east of Carnarvon, is a sandstone plateau that the Western Australian parks service, Explore Parks WA, describes as 12 to 25 km wide and about 75 km long, rising 80 m above the surrounding red plain, with rocks that formed beneath an ancient sea. Mookaite is mined from small sites, which the Stocklmayers locate north of the Gascoyne River on the western margins of the range.

The colors arrived much later than the rock. Geology.com explains that in one area along Mooka Creek the Windalia Radiolarite is exposed at the surface, and there groundwater stained it red, maroon, purple, white, cream, yellow and brown. The radiolarite is widespread in the basin, but the brightly stained, well-silicified ornamental stone comes only from that weathered, near-surface zone. The rock was named after the creek.

Is mookaite really jasper?

By trade usage, yes; by strict geology, it is a chert. Geology.com points out that the same hand specimen might be called chert by one person, flint by another and jasper by a third, depending on background and use. It describes "jasper" as more of a gemological term than a geological one: it is what lapidaries call opaque microcrystalline quartz chosen for color, pattern and polish. Minerals.net defines jasper as an opaque variety of chalcedony, usually brown, yellow or red.

Mookaite fits the lapidary meaning exactly, so "mookaite jasper" is a fair descriptive name. It is also one of the more honest names in a crowded field: unlike several jasper trade names covered in the jasper trade names guide, it is real microcrystalline silica rather than a different rock borrowing the word.

A quick check from Geology.com separates microcrystalline from coarsely crystalline quartz: look at a conchoidal fracture surface. Coarse quartz gives a vitreous, glassy fracture; chalcedony and jasper give a duller, subvitreous one. Rough mookaite with chipped edges shows that dull, fine fracture.

How do you recognize mookaite?

The palette is the giveaway. Good mookaite combines mauve or plum with mustard yellow, brick red and cream in one stone, often with soft, cloudy boundaries rather than sharp bands. Other features to look for:

  • Mottled, blotchy patterns. Color follows the groundwater staining, so it spreads in patches and veins rather than in neat agate-style bands.
  • Fine, even polish. The Stocklmayers' point about no directional weakness shows in finished pieces: a good sphere polishes evenly without plucked grain or undercutting.
  • Opaque body. Thin edges may let a little light through, but mookaite is not translucent like agate.
  • Natural variation within a lot. Mixed tumbles range from almost all yellow to almost all purple. A batch of identical tumbles in one bright hue may be dyed.

Minerals.net notes that most jasper is natural and untreated, but occasionally dyed. Dye collects in cracks and pores; check those with a loupe.

What is the mookaite labelling problem?

The difficulty is that "mookaite" is a locality name being used as a color description. Strictly, mookaite is the Windalia Radiolarite from Mooka Creek in Western Australia. Multicolored jaspers and cherts in similar reds, yellows and purples occur in many countries; Minerals.net lists important jasper deposits in India, Russia, Kazakhstan, Indonesia, Egypt, Madagascar, Australia, Brazil and elsewhere. In practice, retail listings use "mookaite" in two different ways:

  1. A material name. The seller means stone from the Kennedy Range, whatever the label says about origin.
  2. A look. The seller means "jasper with the mookaite palette", wherever it was mined.

Those two readings lead to opposite problems. Genuine Australian material can be listed with a wrong or vague origin, often because a wholesale lot passed through several hands. Look-alike jasper from elsewhere can be called mookaite because it matches the colors. A photograph usually cannot tell you which situation you are in, and a hand lens will not either, because both are opaque microcrystalline silica.

What you can do:

  • Ask what "origin" means on the listing. Is it where the stone was mined, or where it was cut, traded or shipped from? Those can be different countries. For what Madagascar's own deposits produce, see the Madagascar origins guide.
  • Treat a non-Australian origin as a flag, not a verdict. It means either the material is a look-alike or the origin is wrong. Both are worth a question.
  • Pay mookaite prices only for documented material. Rough from a named Western Australian source, or a seller with a supply chain they can describe, justifies a premium. A low-priced mixed lot does not.
  • Judge the stone on its own merits. A well-polished, attractive multicolored jasper is a good stone whatever its name.

For how to read and test any locality claim, see locality labels and provenance.

How should you care for mookaite?

Mookaite is a durable stone. It is hard enough to resist everyday scratching, has no cleavage and does not dissolve, so it can be rinsed in warm water with mild soap and dried with a soft cloth. Porous or chalky patches can soak up oils and dirt, so avoid lotions and harsh cleaners on unsealed pieces. Spheres need a stand, since a drop onto tile can chip them.

Mookaite in crystal traditions

In crystal traditions, mookaite is associated with the Australian outback, with adventure and with grounding. These are cultural associations, not mineral properties.

What to look for when you buy mookaite

Color contrast and polish drive price. The most sought-after pieces combine strong mauve or plum with bright mustard yellow and red in one face, set off by cream. A sphere should be round, glassy all over, and free of open pits or dull porous spots; small natural voids filled with chalky material are common and lower value only if they are large. For tumbles, a mixed lot with natural color variation is normal.

Read origin information as described above. The listing below gives its origin as Egypt or Madagascar rather than Western Australia, and the source of individual pieces has not been independently verified, so judge them by appearance, polish and price.

  • Mookaite: currently a 51 mm sphere and large tumbles. The sphere is the better way to judge the full color range and how well the stone has taken a polish.
  • Polychrome Jasper: multicolored jasper in a 2 by 1.5 inch piece and a large 4.5 inch freeform. Its reds, purples and creams make a useful side-by-side comparison with the mookaite palette.
  • Brecciated Jasper: red jasper broken into fragments and recemented, sold as large tumbles, spheres around 51.5 to 53.5 mm and small towers. A good contrast: angular fragments rather than mookaite's cloudy staining.
  • Ocean Jasper: small tumbles and palm stones of Madagascar orbicular jasper, showing how a jasper with a true single-locality name looks very different from mookaite.

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For the wider family of opaque chalcedony, see the jasper guide.

Frequently asked questions

Where does mookaite come from?

Mookaite comes from Mooka Creek, on the western side of the Kennedy Range in Western Australia, east of Carnarvon. It is mined from small sites north of the Gascoyne River, where the Windalia Radiolarite is exposed and stained by groundwater.

Is mookaite a jasper?

In trade terms, yes. Mookaite is silicified radiolarite, a chert made of microcrystalline silica from radiolarian shells. Jasper is a lapidary name for opaque microcrystalline quartz chosen for color and polish, so mookaite fits the description and is commonly sold as mookaite jasper.

How old is mookaite?

The Windalia Radiolarite formed in the late Aptian stage of the Early Cretaceous, when shallow seas covered large parts of Australia. The bright colors came much later, from iron-rich groundwater staining the rock near the surface.

Is mookaite from Madagascar real mookaite?

Strictly, mookaite is the Western Australian radiolarite, so a stone mined in Madagascar would be a look-alike jasper rather than mookaite. A Madagascar label can also mean the origin is simply wrong or refers to where the stone was cut. Ask the seller what the origin means.

Can mookaite go in water?

Yes. Mookaite is hard silica that does not dissolve, so a rinse in warm water with mild soap is safe. Dry it well, and avoid oils and harsh chemicals on porous patches, which can absorb them.

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