Mookaite: Earth's Most Beautiful Ooze?

Fossils and Minerals

Mookaite is a type of radiolarite, and radiolarite is made from radiolarian oozes. Simple as that, end of blog post! 

An uncut slab of mookaite showing nice color variety. I generally prefer the purple and pinkish colors over the yellow tones, but that's just me ;) Pic from mindat.org

Kidding, kidding. This whole saga might be the coolest thing I learned about this year, so I’m going to need to ramble about it a bit more than that. Let’s start with radiolaria, which you may know better as plankton. Teeny tiny plankton, like 0.1 to 0.12 millimeters tiny! These little single celled beasties have the most beautiful and intricate skeletons and they are usually made of silica. They have been living in Earth's seas and oceans for over 500 million years.

That’s right.

Five. Hundred. Million. Years.

They have also been doing a lot of dying over all those millions of years, and those little silica skeletons built up on the sea floor and became.....a siliceous ooze called radiolarian ooze!! Yup, ooze is a real Science Word and it basically means a layer of sediment on the ocean floor that consists of the remains of microorganisms rather than just inorganic mud. 

An assortment of radiolarians from usgs.gov

Ok, so we have our dead radiolarian mud building up in a nice thick layer on the ocean floor, but as we know, things are always moving and shifting on this planet so eventually our ooze gets buried by other sediments. The pressure and temperature begin to build as they are buried and all those individual skeletons begin to cement together into a nice sedimentary rock called radiolarite! 

Mooka Station, where mookaite is mined. Pic from mindat.org

But not all radiolarites are mookaite! Radiolarite can be found in many places around the world, but only one place gives us mookaite, the Windalia Radiolarite formation. Cut to Western Australia, 125-113 million years ago. A shallow sea covers the land and the radiolarians have been doing their thing, but now the water is retreating. The ooze gets buried by other sediments and starts to solidify into rock, but not before all that silica does a little chemical interacting with other minerals in the groundwater like hematite and goethite. Pressure, heat, and chemistry do what they do and the result is.…..mookaite and all it’s glorious colors! The variations in color and intensity are a result of different concentrations of minerals present in the ground water when the material was solidifying.

Other places on earth where radiolarite has formed didn’t have this particular cocktail of minerals interacting in quite the same way so the results just aren't as spectacular.


Radiolarite in California. Cool as heck, but just not as pretty :)

To recap: tiny plankton skeletons made of silica fall to the bottom of the ocean and turn into ooze, which then gets buried in sediment and mixes with minerals in the groundwater, and then turns into stone which happens to be beautiful. I told you it was simple ;)

If all this sounds a bit familiar to you, you might be thinking of the peanut wood blog post. That’s right, peanut wood was formed in the same area and by the same critters as mookaite!

The area where mookaite is mined was home to two groups of Aboriginal people, the Maia and Malgaru, who named the region Mooka or Falling Waters, referring to the abundance of springs feeding into the nearby creek. I recognize and acknowledge Aboriginal people as the traditional custodians of this land. 

I hope you found this journey as fascinating as I did. If you’d like to see what I’ve made with this unique material you can click here.

Thanks for tagging along,

Maranda




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