George Fife Angas, for whom the mineral was named, was the son of an English coachbuilder and ship owner, who did not
visit Australia until he emigrated there at the age of seventy. Throughout his life he was a dedicated
non-conformist Christian, and this drove his approach to promoting social reforms. Although he was based in England,
he was heavily involved in the then Province of South Australia, colonised by the British government, long before he
actually visited it. He invested in it, supported the rights of aboriginal Australians, and eventually died there.
He was a good man, and the mineral community can be glad that he has a mineral named after him.
Images
Formula: CaMgAl2(PO4)2(OH)4.7H2O
Hydrated phosphate with hydroxyl
Crystal System: Amorphous, formerly thought to be crystalline because of admixture with crystalline phases
such as elliottite
Specific gravity: 1.57 measured
Hardness: 2
Streak: White
Colour: Snow-white
Environments
Metamorphic environments
Hydrothermal environments
Angastonite was approved in 2008 and redefined as an amorphous mineral in 2021; to date (July 2023)
it has been reported only from the type locality.
Localities
At the type locality, the Penrice marble quarry, Penrice, Barossa Valley, North Mt Lofty Ranges, South Australia,
angastonite occurs in phosphate mineralisation in a gossanous
weathered zone above marble as snow-white crusts and coatings up to
1 mm thick. Associated minerals include minyulite,
perhamite, crandallite and
fluorapatite
(MM 72.1011-1020, HOM).
The angastonite is formed from incongruent leaching of minyulite
in circulating magnesium- and calcium -bearing solutions. The amorphous phase undergoes local recrystallisation to
form penriceite and two other new
crandallite-derivative layer phases
(EJM 34.2.215-221).
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