Images
Formula: Ca2(PO3OH)(SO4).4H2O
Compound phosphate
Crystal System: Monoclinic
Specific gravity: 2.30 to 2.34 measured, 2.32 calculated
Hardness: 1 to 1½
Streak: Pale yellow
Colour: Light yellow, yellow, brownish yellow, colourless
Environments
Ardealite occurs in limestone caves, as a
secondary mineral formed at an early stage of the breakdown of
bat guano, in reaction with calcite. Associated minerals include
brushite, gypsum,
carbonate-rich hydroxylapatite,
newberyite and taranakite
(HOM).
Localities
At the type locality, the Cioclovina cave, Boșorod, Hunedoara, Hunedoara, Romania, ardealite is found in
phosphate earth deposits associated with gypsum and
brushite
(AM 17.251). The ardealite derives from the reaction between calcium carbonate from the moonmilk flows
or the cave floor and phosphoric solutions derived from bat guano, with or without
hydroxylapatite as a precursor, at pH values up to 5.5
(EJM 29.1055-1066).
The Măgurici Cave, Sălaj, Romania, hosts a diverse assemblage of minerals. The phosphatisation of
illite and montmorillonite
clay-rich sediments, located on the cave's floor, lead to the formation of
taranakite and francoanellite.
Mineral assemblages precipitated at the boundary between limestone
bedrock and guano deposits are dominantly hydroxylapatite,
brushite, ardealite and
monetite. A number of sulphate minerals, such as
gypsum, bassanite,
mirabilite and cesanite, were
precipitated along with the phosphates
(EJM 15.741-745).
Back to Minerals