This is the cluster of brown staurolite crystals with garnet crystal. Dimensions: 3.3 x 1.8 x 0.7″ (8.4 x 4.5 x 1.9cm). Weight — 3.8oz (107 grams). Origin: Russia, Siberia.
Some information about staurolite:
Staurolite is a reddish brown to black, mostly opaque, nesosilicate mineral with a white streak. It crystallizes in the monoclinic crystal system, has a Mohs hardness of 7 to 7.5. Magnesium, zinc and manganese substitute in the iron site and trivalent iron can substitute for aluminium.
Staurolite often occurs twinned in a characteristic cross-shape, called cruciform penetration twinning.
The name is derived from the Greek, stauros for cross and lithos for stone in reference to the common twinning.