Staurolite


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Related to Staurolite: sillimanite

staurolite

[′stȯr·ə‚līt]
(mineralogy)
FeAl4(SiO4)2(OH)2 A reddish-brown to black neosilicate mineral that crystallizes in the orthorhombic system, has resinous to vitreous luster, hardness is 7-7.5 on Mohs scale, and specific gravity is 3.7. Also known as cross-stone; fairy stone; grenatite; staurotide.

Staurolite

 

a silicate mineral with the chemical composition Fe2+Al4[Si04]2O2(OH)2. Admixtures of Co, Ni (lusakite variety), and Mn (nordmarkite variety) frequently occur.

Based on the structure of the crystal lattice, staurolite belongs to the silicate class having isolated tetrahedral [SiO4]4- groups joined through Fe2+ or Al3+ cations in fourfold or sixfold coordination; the excess bonding orbitals are compensated by additional O2- and (OH)- anions. Staurolite crystallizes in the mono-clinic (pseudorhombic) system, forming either separate short prismatic crystals dark brown in color or, more frequently, cruciform twins. Staurolite’s hardness on Mohs’ scale is 7–7.5, and the density is 3,650–3,770 kg/m3. The color may be dark red, brown, brown-black, or yellow-brown, and the luster is vitreous.

Staurolite is an accessory mineral in schists (together with kyanite, garnet, and andalusite) and gneisses. Its rare transparent crystals are sometimes used as gems.

References in periodicals archive ?
Sector-hourglass zoning--Sector-hourglass zoning typically occurs in chloritoid, and less commonly in biotite and staurolite (Fig.
Fieldwork was primarily focused on localities with staurolite in pelitic schists from the Silgara Formation as previously reported (Rios et al., 2003; Garcia et al., 2005) and the sampling strategy focused on taking staurolite-bearing samples from several outcrops.
and Shaykhbaglou, S.: 2015, Crystal size distribution of kyanite and staurolite from Hamza Qassim and Khazai Bala Metapelites--Southeast Shahin-Dezh.
Neither garnet nor staurolite has been observed in the nearly 200 thin sections of metamorphic samples we have studied.
Biasill, which is a slightly finer grade of staurolite sand, has a low coefficient of thermal expansion and high thermal conductivity with an AFS grain fineness number of between 66 and 75 (Fig.
For example, Georgia's state rock is staurolite, and quartz crystal is the state gem.
The minerals in sand ate 93% to 96% quartz, opaque heavy minerals between 3% - 5% and the remaining 1% - 3% minerals in decreasing order, muscovite, homblende, chlorite, tourmaline, staurolite, garnet, andalusite, biotite and zircon.
The MPH sample was dominated by diopside and hornblende; RSB by epidote, garnet, and biotite; and SQB by rutile, epidote, staurolite, and apatite.
The metamorphosed alteration zones are characterized by the presence of various combinations of anthophyllite, cordierite, garnet, staurolite, biotite and/ or andalusite.
Different kinds of mineral alterations taking place in the Devonian sequence during post-sedimentary processes have been studied: formation of authigenic leucoxene, anatase, apatite, pyrite, and goethite, dissolution of garnet, staurolite and kyanite, replacement of magnetite, amphiboles, titanium-bearing minerals and feldspar, formation of authigenic overgrowths of detrital feldspar grains (Kleesment & Paap 1978; Kleesment 1984, 1998).