Of all the flakeable stone available to the modern knapper, Mookaite (sometimes spelled Mookite) is arguably one of the world’s most aesthetically pleasing lithic raw materials. Given its popularity in the US, almost all CHIPS readers would have heard of or seen a point made out of Mookaite. In fact, many readers have probably made points out of it before! For those of you who own a copy of the Art of the Ancients, 2004 Flintknapping Calendar, you need only turn to Don Roberts’ work (September) to see some beautiful examples of Mookaite points. These statements aside, the vast majority of knappers, both in the US and elsewhere, know very little about this enigmatic Australian stone-type. Ask your average knapper about Mookaite and nine times out of ten you will get the following standard response: “I think it comes from Western Australia.” Your chances of getting any more information than this are slim to none! It’s not just knappers either; most of the geologists consulted during my research could only provide basic information on Mookaite, such as general source areas and brief descriptions. In light of these comments, the following article aims to remove some of the mystery surrounding Mookaite by providing CHIPS readers with a brief introduction to this stone type. In this short article, I will discuss Mookaite’s geological origins, its distribution in Western Australia and its best known source (i.e Mooka Station). In addition to this, I will provide contact details for an Australian Mookaite supplier. Significantly, the information in this article has been drawn from geological and gemstone publications as well as personal conversations with geologists, rock hounds and land owners.

The term ‘Mookaite’ is an unofficial, locally coined name for a silicified porcelanite which forms in the weathering profile of a geological formation known as Windalia Radiolarite (WR), a Lower Cretaceous siltstone that outcrops over much of the Carnarvon Basin in Western Australia, Fig. 1. Depending on who you talk to or which book you read, Mookaite is variously described as chert, opalite, chalcedony or combinations of the three. From a strictly geological perspective however, Mookaite is best defined as a silicified type of WR whose silification is opaline to chalcedonic.

Although WR’s precise age has not yet been determined, current estimates put the formation at 105 to 115 million years old. WR has been classified as a shallow-marine deposit in onshore areas and is known to have been associated with a major flooding of the Australian continent by the sea. At depth, WR is medium to dark grey in color, however, in outcrop it is often leached and exhibits irregular patches of color ranging from white through to various shades of yellow, red, purple and brown (Mookaite as we knappers know it!). These colors are due to differing amounts of iron and manganese contamination in the rock. Importantly, Mookaite has no cleavage and will usually break with a smooth, conchoidal fracture. Mookaite pieces occasionally contain relatively large fossils, most of which are easily identifiable. On the same note, some pieces exhibit cavities partially filled with crystals of clear quartz and other colorless minerals.

Without going into any detail, microscopic examination of Mookaite has revealed that it is a somewhat unique rock type. It consists largely of microscopic organisms known as Radiolarians, which possess an unusual skeletal structure made up of opaline silica. According to Morrison, “Billions of these were deposited, as sediment, in the shallow, near shore area of ancient seas, together with remains of other sea creatures such as forams, pelecypods, ostracods, ammonites and belemnites. When the seas retreated, these sediments were cemented into solid rock by silica, carried in groundwater, either from the radiolaria themselves or from weathered rocks nearby. Often the calcite of the larger fossils is dissolved away, leaving only the mould to show where the organic remains had been. The type and degree of silicification varies from place to place, forming rocks now called opalite, chert and chalcedony.”

Lastly, for those of you who are interested, and I’m guessing there must be some rockhounds out there, Mookaite’s hardness varies with the degree of silification but is generally a 6 or 7 on Mohs’ scale. The rock’s specific gravity varies from approximately 2.62 to 2.66.

In terms of its distribution, Mookaite can be found in most areas where WR outcrops. This said, the main (or at least best known) locality for Mookaite is on Mooka Station, a former sheep station situated at the southwestern end of Western Australia’s Kennedy Range, Fig. 2. On Mooka Station, Mookaite is known to sporadically outcrop over an area of approximately 75 acres. The main outcrop of Mookaite on the station forms a cliff beside a perennial creek known locally as Binthabuka or Mooka Creek. According to Morrison, “…three slight differences in rock type can be distinguished” at the main outcrop. One area consists of ‘sunset opal’, a pale yellow opalite with swirls of other pale colors within it. Morrison does not include sunset opal under the general term of Mookaite, however, most of the geologists and rockhounds I spoke to do not make the same distinction. The central portion of the outcrop consists of massive chert with silica contents ranging from 85-99%. Significantly, some areas are less silicified than others and are rather porous in nature. The third variety of Mookaite at the main outcrop consists of large rounded nodules, usually with dark reddish centers surrounded by lighter colors. Unofficially, these nodules have been classified as chalcedony.

Discussions with Alan Butler, whose sister Leanne and brother-in-law Robert are currently the caretakers of Mooka Station, have revealed that Alan’s father, Ron Butler, put the first mineral claim over the station’s Mookaite deposits in 1964/65, (Mr. Butler could not recall the exact date). Since this time, Alan and other family members have sporadically mined the station’s Mookaite deposits, focusing their efforts on extracting the rock from the creek bed using backhoes. Over the years, the Butler Family have sold parts of their original mining claim to other mining parties. Between these parties (two of whom are still active), hundreds of tons of Mookaite have been extracted from the station’s deposits. From Mooka Station, Mookaite has been sold and traded across the world.

In conclusion, I hope that CHIPS readers have found this article both interesting and informative. I would like to finish by pointing out who CHIPS readers should get in contact with should they wish to obtain some high-quality Mookaite for knapping:

Alan Butler

25 Pleasant Grove Circle

Falcon, W.A.

Australia, 6210

Bracewell, H.

Gems Around Australia – Part 13. Australian

Gemmologist 19. pp. 467-470.

Geological Survey of Western Australia

1994 Gemstones in Western Australia. Perth: Geological Survey of Western Australia.

Hocking, R, M., Moors, H. T. and W. J. E. Van De Graaf