Staurolite

Staurolite is a red 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 and a rather complex chemical formula: (Fe,Mg,Zn)₂Al₉(Si,Al)₄O₂₂OH₂. Iron, magnesium and zinc occur in variable ratios. Image File history File links Staurolite. ... Image File history File links Staurolite. ... The silicate minerals make up the the largest and most important class of rock-forming minerals. ... This article is about minerals in the geologic sense; for nutrient minerals see dietary mineral; for the band see Mineral (band). ... In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ...

A special property of staurolite is that it often occurs twinned in a characteristic cross-shape. The macroscopically visible crystals are of prismatic shape. They are often larger than the surrounding minerals and are then called porphyroblasts. A twin boundary occurs when two crystals of the same type intergrow, so that only a slight misorientation exists between them. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ...

The name is derived from the Greek, stauros for cross and lithos for stone in reference to the common twinning. Staurolite is a regional metamorphic mineral of intermediate to high grade. It occurs with almandine garnet, micas, kyanite and other metamorphic minerals. Metamorphism can be defined as the mineralogical, chemical and crystallographic changes in a solid-state rock, i. ... The Garnet group of minerals show crystals with a habit of rhombic dodecahedrons and trapezohedrons. ... rock with mica Mica sheet mica flakes The mica group of minerals includes several closely related materials having highly perfect basal cleavage. ... Kyanite The mineral kyanite is an aluminium silicate of the sillimanite group (along with andalusite and sillimanite), also called alumino-silicate. ...

References

• Webmineral
• Mindat w/ locations
• Mineral galleries