Cafarsite

cafarsite

asbecasite

chernovite

synchysite

Images

Formula: (Ca,Na,☐)19Ti8Fe3+4Fe2+4(AsO3)28F
Arsenite, titanium-bearing mineral
Crystal System: Isometric
Specific gravity: 3.9 measured, 3.5 calculated
Hardness: 5½ to 6
Streak: Yellow-brown
Colour: Dark brown
Environments

Metamorphic environments

Localities

At the Monte Cervandone area, Devero Alp, Baceno, Verbano-Cusio-Ossola Province, Piedmont, Italy, cafarsite was found on the Wannigletscher in association with asbecasite. It is the most famous of the rare arsenic species from Monte Cervandone, known in collector-quality specimens from no other locality in the world.
Cafarsite typically appears dark brown or black, but is actually a very dark red. Some altered cafarsite crystals show coatings of green agardite-(Y). Cafarsite is almost always associated with smoky quartz, clinochlore and tourmaline; other common associations include asbecasite, chernovite and tilasite. Fine cafarsite specimens have been found all around the region, in crystals rarely as large as 3 cm but exceptionally reaching 9 cm. These include some small crystals which are deep red and transparent, as well as a very few pieces with associated yellowish to pink fluorite crystals.
Good cafarsite has also been found in the Lärcheltini Zone, in some cases the cafarsite crystals have anatase crystals perched on them, indicating that the cafarsite predates at least some of the anatase. Clefts in the Mättital area have produced weathered brown cafarsite crystals to 1 cm, some with olive-green coatings of metakahlerite (MinRec 56.3.301-309).
Cafarsite from the Monte Cervandone area - Image

At the type locality, the Wanni glacier - Scherbadung area, Binn, Goms, Valais, Switzerland, cafarsite occurs on cleft faces in orthogneiss associated with asbecasite, gasparite-(Ce), chernovite and synchysite (HOM).
Cafarsite from the Wanni Glacier - Image

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