#inosilicates

[mineralogasm]

Pargasite in Marble from Luc Yen, Yen Bai Province, Vietnam

Size: 5.8 x 4.7 x 2.6 cm

[rocksncrystals-blog]

429 Hornblende

weight 33g/165cts & dimensions 33x37x14mm

[mineralogue-blog]

Babingtonite is an dark green to black inosilicate mineral represented by the chemical formula Ca2(Fe,Mn)FeSi6O14(OH). It is opaque but translucent in thin splinters or crystals, and it has a Mohs hardness of 5.5-6. It contains both Fe2+ and Fe3+ ions, which causes it to be weakly magnetic. It occurs in veins cutting through granitic pegmatites, in cavities and vugs in mafic volcanic rocks and gneisses, and in skarns. It is commonly associated with zeolites, although it is somewhat rare. Its presence in a mineral sample tends to raise its value.

Sources:

Mindat

Wikipedia

Amethyst Galleries  

Images: Two samples of babingtonite with prehnite from Hongquizhen Quarry, Liangshan Autonomous Prefecture, Sichuan Province, China. From irocks.com, 1 and 2.

[mineralogue-blog]

Prehnite is a low-grade metamorphic silicate mineral usually forming as stalactitic, globular, or botryoidal aggregates. It rarely forms crystals. It has a chemical formula of Ca2Al2Si3O10(OH)2. It is translucent and usually colourless, grey, yellow to yellow-green, or white. A rare orange variety was discovered at the Kalahari Manganese Fields in South Africa.

Prehnite has a Mohs hardness of 6-6.5 and a specific gravity of 2.8-2.95. Prehnite fluoresces blue-white or mild peach under short UV radiation and yellow under longwave UV. It has a colourless streak. It is classified under two different silicate structures: inosilicate by the Strunz classification scheme, where it is stated that the mineral is transitional between the inosilicate “chain silicate” structure and phyllosilicate “ring silicate” structure, and phyllosilicate by the Dana scheme, under sheet silicates with four-membered rings.

Sources:

Wikipedia

Mindat

Webmineral

Image: Prehnite from Sadiola Hill, Kayes Region, Mali. Source: irocks.com