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Formula:KAl2(PO4)2F.4H2O
Hydrated phosphate containing halogen
Specific gravity: 2.47
Hardness: 3½
Streak: White
Colour: Colourless, white, greenish yellow; colourless in transmitted light.
Solubility: Readily soluble in warm dilute NaOH and in hot concentrated hydrochloric and sulphuric acids, and slowly soluble in
warm dilute nitric acid (AM 18.512).
Environments
Minyulite is commonly associated with wavellite and
fluellite, and less commonly with aldermanite,
saléeite, crandallite,
leucophosphite, cacoxenite and
tinsleyite (AJM 17.1.22), and also with
dufrénite, apatite and
variscite (HOM).
Localities
At Wolffdene quarry, Logan City Shire, Queensland, Australia, minyulite occurs with fluellite
(Dana).
At the Moculta quarry, Angaston, Barossa Valley, Mount Lofty Ranges, South Australia, minyulite is found growing on
apatite and associated with fluellite
(AJM 17.1.22).
The phosphate minerals are closely associated with magnesium-bearing
limestone/marble,
and minyulite is commonly found to be altered to amorphous angastonite.
Minulite here is unstable in the presence of near-neutral Ca2+ and Mg2+ bearing solutions,
and decomposes with loss of potassium and fluorine to form amorphous
angastonite. This amorphous phase plays an important role in the paragenesis
of new secondary phosphate minerals including
penriceite and elliottite
(AJM 23.1.21-25).
At Wait's quarry, Noarlunga, Angaston, Mount Lofty Ranges, South Australia, minyulite occurs with
dufrénite in altered outcrops of
glauconite-bearing phosphate beds (Dana).
At the type locality, the Minyulo Well, Dandaragan, Dandaragan Shire, Western Australia, minyulite occurs filling
minute veins
or cavities in a highly phosphatic ironstone bed made up of
limonite, quartz,
dufrénite, apatite and
glauconite (AM 18.512), associated with
wavellite, variscite,
leucophosphite, glauconite,
fluellite, dufrénite and
apatite (Mindat)
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