Mookaite is a colourful rock whose correct geological name is windalia radiolarite. It's a cryptocrystalline sedimentary rock that's made up predominantly of the microscopic remains of minute aquatic organisms called radiolaria which measured just 0.1 to 0.2 millimetres is size. The radiolaria which produced intricate mineral skeletons died as the ancient oceans receded and over time were slowly transformed into sedimentary rock. Although different varieties of radiolarite can be found around the world, windalia can only be found in one location in Western Australia.
The stone which was named locally as Mookaite is a jasper that can only be found on Mooka Station which was once a sheep farm which lies to the west side of the remote and rarely visited Kennedy Range National Park in Western Australia. The location of the mookaite deposit is on privately owned land which means it cannot be mined by anyone.
Mookaite is often incorrectly spelt and it's not unusual for it to be referred to by several different names all of which strangely, are very similar. Some of these include Mookalite, Mook, Mookerite and Mook Jasper. Although often referred to as a mineral Mookaite is actually a rock because like most jaspers, it's made up of a number of different minerals and other materials.
Although this Australian jasper is well known as Mookaite, the name has never been officially registered. Along with opal, Mookaite is one of Australia's best known gemstones. The finest grade material can boast impressive colour and markings and can take on a high polish. Despite its popularity as a lapidary material it is quite brittle hence can fracture easily so it should always be handled carefully. The colours in Mookaite are caused primarily by the presence of iron and manganese.
On Mohs scale of mineral hardness Mookaite grades 6 to 7.
Mining for Mookaite