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Formula: Ca9Fe3+(PO4)7
Anhydrous posphate, merrillite group,
cerite supergroup
Crystal System: Trigonal
Specific gravity: 3.09 calculated for the empirical formula
Hardness: 4½
Streak: White with a yellowish tint
Colour: Light yellow and light brown
Environments
Deynekoite is a new mineral, approved in 2022 and to date (February 2024) reported only from the type
locality.
Localities
At the type locality, the Deynekoite type locality, Daba-Siwaqa complex, Transjordan Plateau, Amman Governorate,
Jordan, deynekoite was found in paralava. The
paralava, consisting of
diopside, tridymite,
anorthite, wollastonite and
fluorapatite, is enriched in
iron-bearing phosphides and phosphates at the contact with the altered country
rock. Cristobalite overgrowing
tridymite has a fish-scales texture indicating that temperature of the
paralava could have reached 1500°C. Deynekoite forms
transparent, light yellow or light brown grains up to 40 μm in size.
The formation of phosphides on the boundary of the paralava and
country rock occurred at temperatures above 1300°С. With decreasing temperature and increasing oxygen activity,
phosphides are replaced by Fe2+-bearing phosphates. Deynekoite, which contains Fe3+
(substituting for Fe2+ phosphates) and a small amount of water, formed at temperatures of 600 to 800°C
(MM 87.943-954).
Minerals associated with deynekoite include zuktamrurite,
yakubovichite,
transjordanite,
orishchinite, nickolayite,
nazarchukite, murashkoite,
moabite and crocobelonite
(Mindat).
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