Piz Grisch, Ausserferrera, Ferrera, Viamala Region, Grisons, Switzerlandi

Regional Level Types
Piz Grisch	Mountain
Ausserferrera	Village
Ferrera	Municipality
Viamala Region	Region
Grisons	Canton
Switzerland	Country

Piz Grisch is a mountain of the Oberhalbstein Alps, overlooking Innerferrera in the Swiss canton of Graubünden. A small glacier lies at the base of its northern face, the Glatscher da Sut Fuina.

Metamorphosed Cu-Bi mineralisation located in the face under the ridge extending to the northwest of Piz Grisch (3062 m; Swiss coordinates: 756.050/155.345).

The occurrence is the type locality for pizgrischite, which is the main metallic mineral in dm-size pods within a massive to saccharoidal quartz vein (0.5-2 m in thickness) that runs semi-parallel to a siderite vein (up to 5 m in thickness). Both veins can be followed along strike for about 80 m, and are embedded in augen gneisses belonging to the pre-Triassic basement (Roffna Porhyry Complex) of the Surreta nappe.

The coordinates of the type locality according to the Swiss federal system are: 755.400/155.700; 2950 m. The access to this mineral occurrence is made difficult by its location in a cliff face, and climbing is necessary. However, mineralised blocks, fallen from the veins, can sometimes be found underneath, on the Glatscher da Sut Fuina.

Pizgrischite occurs as blades up to 1 cm in length. They are metallic lead grey, thin, opaque and striated, forming sprays embedded in fine-grained saccharoidal quartz. This rich occurrence of an acicular sulfosalt was mentioned already by Grünenfelder (1956), who identified it as "wittichenite" on the basis of its optical properties.

Other associated sulfides and sulfosalts (tetrahedrite, chalcopyrite, pyrite, sphalerite, emplectite, and derivatives of the aikinite-bismuthinite series) form mm-sized masses dispersed in quartz.

In particular, xenomorphic Bi-bearing tetrahedrite is commonly partially replaced by flame-like inclusions of emplectite and idiomorphic hammarite ± friedrichite. Some isolated grains, also embedded in quartz, consist of krupkaite ± lindströmite, admixed with minor emplectite. Chalcopyrite, pyrite and rare sphalerite complete the primary association of metallic minerals.

The first stage of alteration by meteoric water led to the formation of covellite and digenite along cleavages and cracks of pizgrischite or associated sulfosalts. Bismutite and malachite are common, and azurite is rare in the second stage of alteration.

Some crystals of pizgrischite are completely replaced by a mixture of bismutite and malachite.

The siderite vein consists of manganoan siderite and ankerite with accessory hematite and rare pyrite and chalcopyrite.

Other Databases

Wikipedia:	https://en.wikipedia.org/wiki/Piz_Grisch
Wikidata ID:	Q664661

Other Regions, Features and Areas containing this locality

References