Mount Francisco, Mugarinya Community, Port Hedland Shire, Western Australia, Australiai

Regional Level Types
Mount Francisco	Mountain
Mugarinya Community	Community
Port Hedland Shire	Shire
Western Australia	State
Australia	Country

Mount Francisco and the surrounding area is made up of ultramafic rocks with lesser amounts of amphibolite schist, metabasalts and metasediments. It forms a greenstone roof pendant in the Numbana granite. These metamorphic rocks have been intruded by a number of pegmatites. G.J. Hooley's Columbite Lode on the Numbana pegmatite is the exception, which is a zoned albitic quartz cored pegmatite 15 metres long.

Government geologist E.S. Simpson investigated the site in the early Twentieth Century, reporting on several species, without detailing the exact lease at Mount Francisco.

Some specimens have been seen, probably collected in the 1970's, after an expedition to the area by the WA Government Chemical Laboratories, and the location was explored by Government Geologist E.S. Simpson in the early 20th Century.

This includes pebbles of native bismuth covered with yellow bismutosphaerite, together with manganocolumbite pebbles. A few flakes of molybdenite, associated with quartz, and dendritic films of ferrimolybdenite. Gravelly ilmenite probably derived from a pegmatite.

Spinel nodules from an ounce to up to a pound in weight in a narrow greenstone belt at Mount Francisco, dark green, transparent in thin section, accompanied by chlorite, talc, biotite, olivine, hypersthene, magnetite, ilmenite and apatite. Numerous large octahedral magnetite crystals are found in a pegmatite vein near the spinel. Upper parts have converted to martite. Stream tin is also found a few miles to the south, contaminated by pea sized magnetite.

Rutile has been found as a few small specks. Many cassiterite crystals from simple bipyramidal or combinations with 101. The crystals show distortion of elongation parallel to the pyramid edge.

Beryl as well shaped crystals, pale green colour, 1 ounce to 50 lb in weight, in a columbite pegmatite.

H. Bowley (Assistant Government Mineralogist) identified helvite at Mount Francisco, being the first discovery of the mineral in Western Australia.

Vesuvianite as dense drusy masses, olive brown in colour, granular passing inwards into dense radiating masses, and then short prisims 100, 110 and 001. Lepidolite as large bunches fine and scaly. Manganocolumbite described as plentiful from the Hooley's location. Tanteuxenite as imperfect tabular orthorhombic crystals, resinous lustre, light to dark brown, associated with cassiterite. Monazite as small brown water worn pebbles in alluvial cassiterite. Crystals up to 0.5 inches not uncommon.

Large masses of lithiophilite altered near surface to black masses of purpurite and psilomelane. Unaltered it has a pale grey colour and translucent, but weathers to amber yellow, then brown with blood red flakes (pure purpurite), and finally black by the psilomelane staining.
Apatite as narrow veins, white or pale grey in lithiophilite masses.

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References