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Formula: CaMg2(AsO4)2.2H2O
Valence: CaMg2(As5+O4)2.2H2O
Hydrated arsenate,
tsumcorite group
Crystal System: Monoclinic
Specific gravity: 3.89 measured, 3.73 calculated
Hardness: 5
Streak: White
Colour: Light brownish to salmon-pink or orange-brown
Luminescence: Not fluorescent under UV
Common impurities: Mg may be replaced by minor Al and Fe3+
Environments
Sedimentary environments
Metamorphic environments
Localities
The type locality, Falotta, Tinizong, Surses, Albula Region, Grisons, Switzerland, belongs to the numerous
manganese occurrences embedded in the
radiolarites which overlay
basalts in the Swiss Alps. The sedimentary ores recrystallised during the
regional Alpine metamorphism under lowest
greenschist facies conditions. The ore today consists
mainly of braunite, rhodonite and
spessartine. In addition,
tinzenite, parsettensite,
sursassite and strontium-bearing
piemontite are locally abundant.
At Falotta, arsenic-bearing minerals occur in several types of veins. The types
are:
(1) Massive brandtite/sarkinite
veinlets with minor manganberzeliite and
grischunite.
(2) Small open fractures containing free crystals of tilasite,
kemmlitzite, bergslagite and
geigerite, together with quartz and
albite.
(3) Thin open fractures and quartz or carbonate veinlets, which occur in a very
altered, cohesion-poor ore, and which host cabalzarite
Cabalzarite, like the other As-minerals of Falotta, results from the hydrothermal remobilisation of As during the
retrogradation of the Alpine metamorphism.
Although the occurrence of cabalzarite is restricted to a 1 m2 outcrop in the Falotta mine, the mineral
displays a broad range of morphologies:
(1) Isolated crystals up to 1 mm in size. The largest crystals look like
axinite
(hatchet-like), and their faces are often curved.
(2) Complex polycrystalline aggregates, up to 2 mm in length, located in vugs.
(3) Fibrous to tabular crystals up to 3 mm in length, forming radiating aggregates up to 5 mm across. These aggregates
are developed in two dimensions within thin fractures, and formed spheroids where sufficient space was available.
(4) Aggregates of parallel needles filling veinlets up to 2 mm thick, associated with massive
quartz, carbonate, and fibrous
sursassite. Here, cabalzarite may be mistaken for
sursassite.
In vugs, cabalzarite is associated with crystals of quartz,
adularia, kutnohorite,
tilasite, grischunite and
arseniosiderite, with sprays of fine needles of
tripuhyite and with black crusts of manganese oxy-hydroxides
(ranciéite-takanelite).
Arsenogoyazite is apparently a common but easily overlooked mineral
associated with cabalzarite; it occurs as xenomorphic grains in cabalzarite, as white veinlets up to
several millimeters in width, and as rare pseudo-rhombohedral crystals in vugs
(AM 85.9.1307-1314).
Cabalzarite from Falotta - Image
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