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Formula: H2K(PO4)
Anhydrous phosphate
Crystal System: Tetragonal
Specific gravity: 2.23 calculated
Hardness: 1 to 2
Streak: White
Colour: White
Solubility: Soluble in cold water
Environments
Archerite occurs as a component of stalactites and crusts on the walls of caves containing bat guano
deposits. Associated minerals include biphosphammite,
aphthitalite, halite,
syngenite, stercorite,
oxammite, weddellite,
whitlockite, guanine,
newberyite, calcite and
mundrabillaite
(HOM).
Localities
At the type locality, the Petrogale Cave, Madura Roadhouse, Dundas Shire, Western Australia, dry pulverulent guano
covers the cavefloor except in the end chambers where convoluted crusts of
aphthitalite and other minerals also occur. The walls are coated with
dark crystalline crusts, in places forming stalactites up to 12" in length. These are mainly composed of
biphosphammite. All fresh guano is devoured by coprophagic insects,
which produce the guano dust. The crusts appear to have originated at a time when the bat population was very large.
The stalactites form roosting places for the bats and these could still be growing from the crystallisation of
urinary deposits from the bats, even in their present small numbers. The rear chambers of the cave were at a
temperature of 20.5°C and 68.5% humidity.
Minerals associated with the biphosphammite and archerite
include aphthitalite, halite,
syngenite, stercorite,
oxammite, weddellite,
whitlockite, guanine,
newberyite and calcite from the
wall rock. The stalactites are mainly composed of biphosphammite.
Archerite occurs on only a few samples in the form of small tetragonal crystals up to 2 mm in length and
crusts of a buff to clear colour. The specimens containing archerite are stalactites, with minor amounts
occurring in the convoluted wall crusts
(MM 41.33-35).
Archerite from the Petrogale Cave - Image
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