Warriedar tourmaline deposit (Mongers Lake), Warriedar Station, Yalgoo Shire, Western Australia, Australiai

Regional Level Types
Warriedar tourmaline deposit (Mongers Lake)	Deposit
Warriedar Station	- not defined -
Yalgoo Shire	Shire
Western Australia	State
Australia	Country

(Map- Google Maps does not show the island. Mindat location approx. based on site visit).

A normally dry salt lake called Mongers Lake is found in the far south-western portion of Yalgoo Shire. This relatively thin salt pan stretches some 200 kilometres in a south and south-eastern direction. In the northern portion of the lake, 7 kilometres east north-east of the abandoned Warriedar Homestead, a hill forms an island in the middle of the lake. The island is almost entirely composed of schorl tourmaline, with some white quartz bands through it.

The tourmaline was discovered in 1962 by prospector Gerry Knorreck. In 1986 2.5t of material was retrieved from the island for testing. The tests concluded the rocks were lapidary grade opaque black microcrystalline schorl, black and white finely mottled schorl and quartz. It is a Mg-Fe rich tourmaline of the dravite-schorl series. In 1994, further tests were carried out by Diamond Mine Holding Pty Ltd, with further studies on the geology of the area in the late 1990's. In 2002-2003, 34t of material was removed, some of which was carved revealing the material can be turned into high quality ornamental jewellery and figurines of a uniform black colour and high lustre.

The rock does not form crystals but is massive. The material is informally known locally as warrierite after the station it is found on. Rocks on the island are of three types:
1. 'Warrierite as a hard (7.0-7.5 Mohs scale) black massive, well jointed, microcrystalline tourmaline with a distinctive conchoidal fracture, as large prismatic or tabular boulders.
2. Tourmalite as the dominant rock, hard, mid to dark grey, mottled quartz- tourmaline rock, containing ragged blebs, veins and boxworks of black tourmaline, often distinctively elongate and almost linear.
3. Quartz as white massive veins which have intruded the tourmaline rock in the centre of the island causing extensive brecciation.

It has been suggested the 'warrierite' may have formed from boron-metasomatic replacement of pre-existing Archean volcanic rocks, the boron fluids having entered a shear zone related to a fault, with a later quartz intrusion.

The Warriedar to Fields Find Road passes close to the western shore of the lake, and its a long walk out to the island from here. Please do not consider driving across the lake-bed, as your car will be bogged to the axles.

Other Regions, Features and Areas containing this locality

References