Cooglegong pegmatite field, Shaw River District, East Pilbara Shire, Western Australia, Australiai

Regional Level Types
Cooglegong pegmatite field	Pegmatite Field
Shaw River District	Mining District
East Pilbara Shire	Shire
Western Australia	State
Australia	Country

55 miles ESE of Wodgina.

Rare earth specimens found at this site. Rare earth rocks are the mineral world's equivalent of tofu- bland to look at but interesting once you know what to do with them.

The pegmatite field is located approximately 50 kilometres south-west of Marble Bar, on the Marble Bar to Great Northern Highway Road, and generally east of the Shaw River crossing. The indication in (Jacobson, et. al., 2007), is of pegmatites scattered over a wide area. Named locations include Shaws Patch, just east of the crossing and south of the road (the Mindat co-ordinates); several north of the road and immediately east of Spear Hill as the gadolinite pegmatites; Stutz 1.8 kilometres south-east of Spear Hill; a beryl bearing pegmatite 200 metres east of the Black Range dyke on Coolegong Creek; the Coondina pegmatite field; Five Mile Creek pegmatite field, Elsy's pegmatite field; and several isolated pegmatites between Spear Hill and the Black Range Dyke, a prominent north-north-east to south-south-west range seen to the east. A number could be difficult to locate, with tracks overgrown or non-existent, very old or limited workings, and rare species being small and dull.

The pegmatites have formed in the Coolegong Adamellite and Spear Hill Adamellite, both about 2.8 Ma. The pegmatites are aplite formed within the adamellite. Mining and specimens have come from alluvial diggings, namely Two Mile Creek, Shaw Patch, Coolegong Creek, Spear Hill, the gadolinite group and Stutz's amongst others. They are mineralogically diverse with rare earth species and little studied.

The gadolinite group is possibly the most important on the field. Pegmatite 1 and 2 are located 3 kilometres east of the Coolegong Hotel ruins, and pegmatite 3 a further 3 kilometres east. Pegmatite 3 is also known as Angelo's Gadolinite Vein. They were discovered in 1900, and only pegmatite 3 has been mined; for 1 tonne of gadolinite in 1913, and another tonne in 1920.

Black glassy gadolinite fragments are said to be found on the mullock heaps and near the pegmatites. Masses occur up to 10cm, associated with quartz, albite, and microcline, metamict, nodular, and some have rhombic cross-sections.

One of these pegmatites is the type locality of tanteuxenite-(Y), collected by geologist E.S. Simpson in 1927, and initially described as tantalopolycrase in error.

The pegmatites have produced samples covering the entire fergusonite-formanite series.

Geochronology

Mineralization age: Mesoarchean : 2901 ± 49 Ma to 2839 ± 16 Ma

Important note: This table is based only on rock and mineral ages recorded on mindat.org for this locality and is not necessarily a complete representation of the geochronology, but does give an indication of possible mineralization events relevant to this locality. As more age information is added this table may expand in the future. A break in the table simply indicates a lack of data entered here, not necessarily a break in the geologic sequence. Grey background entries are from different, related, localities.

Geologic Time				Rocks, Minerals and Events
Precambrian
	Archean
		Mesoarchean		ⓘ Cassiterite (youngest age) 2839 ± 16 Ma ⓘ Cassiterite (oldest age) 2901 ± 49 Ma

Other Regions, Features and Areas containing this locality

References