Walstromite

walstromite

sanbornite

taramellite

fresnoite

Images
Images taken under UV illumination show orange (walstromite) and blue (celsian) fluorescence.

Formula: BaCa2Si3O9
Cyclosilicate (ring silicate), margarosanite group, barium-bearing mineral
Specific gravity: 3.67
Hardness: 3½
Streak: White
Colour: Colourless to white
Solubility: Easily soluble in cold dilute acid with the production of a silica gel
Luminescence: Faint pink, white and cream fluorescence under short wave UV; distinct pink, pinkish orange, white or cream fluorescence under long wave UV (Dana). The luminescence centres are Mn2+, Eu2+ and trivalent rare-earth elements (EJM 25.1.71-77).
Common impurities: Ti,Al,Fe,Mn,Mg,Sr,K
Environments

Metamorphic environments

Walstromite occurs in metamorphosed sediments associated with sanbornite, wollastonite, celsian, taramellite, pyrrhotite, pyrite, fresnoite and many other barium silicates (Dana).

Localities

At the Gurim anticline, and at Halamish wadi, both in the Hatrurim Basin, Tamar Regional Council, Southern District, Israel, walstromite occurs disseminated in a sanbornite-quartz gneissic metamorphic rock, especially where the quartz content is high. In small veins of rankinite paralava within gehlenite hornfels. Associated minerals include sanbornite, quartz, wollastonite, celsian, taramellite, pyrrhotite, pyrite, witherite, fresnoite, zadovite, gurimite, rankinite, gehlenite and garnet (HOM).

At the Jakobsberg Mine, Jakobsberg ore field, Nordmark District, Filipstad, Värmland County, Sweden, in a sample of skarn, lead-rich walstromite was associated closely with celsian, phlogopite, andradite, vesuvianite, diopside and nasonite (MM 85.2.224-232).

At the type locality, the Esquire No. 7 claim, Big Creek, Big Creek-Rush Creek Mining District, Fresno county, California, USA, walstromite occurs as individual grains disseminated in sanbornite-quartz rock, especially where the quartz content is high. The layers of walstromite appear to represent original compositional differences in the pre-metamorphic sedimentary rocks. Walstromite also occurs in wollastonite-bearing quartzite that contains little or no sanbornite. Grains up to 12 mm long are not uncommon, and nearly all of the grains contain tiny inclusions of celsian or quartz. The walstromite is associated with sanbornite, quartz, wollastonite, celsian, taramellite, pyrrhotite, pyrite, witherite, fresnoite and an unidentified blue iron-barium silicate mineral (AM 50.318-319).

Rush Creek, Rush Creek deposit, Big Creek-Rush Creek Mining District, Fresno county, California, USA. the area lies within a body of metamorphosed sediments completely surrounded by biotite-quartz diorite. The largest bodies of sanbornite-quartz rock occur at or close to the contacts of the metamorphic and plutonic rocks or entirely within the latter. Some of the smaller bodies of quartz-sanbornite rock are lenses entirely within the metamorphic rocks which are mostly quartzite. In one specimen in which walstromite is present in abundance there are many small crystals of a light green chlorite, ripidolite, and a small amount of pellyite (AM 69.358-373).

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