Minyulo Well, Dandaragan, Dandaragan Shire, Western Australia, Australiai

Regional Level Types
Minyulo Well	Well
Dandaragan	Town
Dandaragan Shire	Shire
Western Australia	State
Australia	Country

Type locality for minyulite discovered July 1932, and described by E.S Simpson and C.R. Le Mesurier. Rare phosphate species. It occurs here as translucent white crystalline aggregates on phosphate ironstone. Rare species dealers have sold material from the site. The best for the species though is Toms Quarry in South Australia. Dandaragan is a small town 150 kilometres north of Perth. The name is Aboriginal for 'good kangaroo country'. It borders the northern limestone heathlands region, and the remnants of the northern Darling Ranges.

The writer looked up the original reference, which was retrieved from the historic archives at the State Library of Western Australia. Government geologist, Simpson, originally found a small amount of material he thought was wavellite. He regretted not collecting more, as back at the laboratory it turned out to be a new species. Described as being on Crown Grant 1110, adjacent to the Minyulo Estate, near Minyulo Well.

The area is described as containing distinct horizontal beds of glauconitic and non-glauconitic sands, clays with a chalk bed on top. At the base of the chalk is a thin bed of nodular apatite. The outcrop studied showed considerable secondary chemical alteration from the decomposition of glauconite and possibly other iron compounds, resulting in the formation of much limonite, found on the surface as iron stained sand, ferruginous sandstone, and hard siliceous ironstone. Some of this iron had taken the place of lime in combination with the phosphoric oxide to produce bright green dufrénite which was plentiful in the outcrop.

The outcrop also contained a small amount of fibrous material in hard phosphatic ironstone carrying partly altered apatite nodules. At the location, minyulite occurs as minute veins and cavities in a highly phosphatic ironstone bed, 3-4 feet thick (original reference imperial), and the horizontal outcrop forms the summit of a low cliff of ferruginous ironstone. The phosphatic rock contains limonite, quartz grains, dufrénite, nodular apatite, and glauconite grains. At the greensand-chalk contact are coprolites (fossilized animal dung, where much of the composition has been replaced by minerals). Above the cliff is a grassy gentle slope of chalk in turn capped by a second bed of limonitised greensand.

Minyulite at the location was described as being distinct crystalline, comprising dense radiating groups of fine fibres, completely filling cavities, or creating mammilliated crusts close to the cavities. In very narrow cavities on flat faces the crystals, 2-5 mm long, form rosettes not unlike wavellite. The species was described as fragile with a hardness of 3.5, specific gravity 2.45 (average from only two specimens), colourless to milky white, translucent, crystals up to 3 mm thick. The type specimen was given to the Western Australian Museum, and a paratype specimen to the British Museum.

Other Regions, Features and Areas containing this locality

References