Formula: Ca6(CO3)1.58(Si2O7)0.21(OH)7[Cl0.50(OH)0.08 (H2)0.42]
Hydrated carbonate containing hydroxyl
Specific gravity: 2.34 to 2.5
Streak: Colourless, also pink
Colour: Colourless (original occurrance), also deep red, rose-brown
Solubility: Dissolves in l:l hydrochloric acid with effervescence
Common impurities: Fe,Mn,Mg
Defernite is a rare carbonate reported from only two sites to date (May 2020)
At the type locality, Güneyce-Ikizdere, Rize Province, Turkey, defernite is a secondary alteration product of high-temperature calc-silicates occurring in skarn at the contact of granite with limestone. Associated minerals include vesuvianite, wollastonite, andradite, diopside, calcite, rustumite, spurrite and hillebrandite (AM 65.1066, Dana).
At the Kombat Mine, Grootfontein, Otjozondjupa Region, Namibia, defernite is distributed through a body of massive, granular hausmannite. Subhedral grains of brucite fill spaces between, or partially include, hausmannite and hillebrandite. Small amounts of crednerite are found within the hausmannite. Native copper is a ubiquitous associate, occasionally forming thin films along multiple cleavage planes in the defernite, and appears to have replaced it in part. Granular baryte, calcite and vesuvianite are also common associates. Crednerite, jacobsite and hematite are less common. Rarely, late-stage veins of calcite were observed intergrown with defernite and arborescent growths of native copper. The defernite-bearing hausmannite ore occurs immediately above glaucochroite- and harkerite-bearing zones (AM 73.888-893).
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