Prehnite 40343 204227010 2008-04-08T15:08:39Z Thijs!bot 1392310 robot Adding: [[es:Prehnita]] '''Prehnite''' is a [[Silicate minerals|phyllosilicate]] of [[calcium]] and [[aluminium]] with the formula: Ca<sub>2</sub>Al(AlSi<sub>3</sub>O<sub>10</sub>)(OH)<sub>2</sub>. Limited Fe<sup>3+</sup> substitutes for aluminium in the structure. Prehnite crystallizes in the [[orthorhombic]] [[crystal]] system. It is brittle with an uneven fracture and a vitreous to pearly lustre. Its [[Mohs scale of mineral hardness|hardness]] is 6-6.5, its [[specific gravity]] is 2.80-2.90 and its color varies from light green to grey or white. It is translucent. Though not a [[zeolite]], it is found associated with them and with [[datolite]], [[calcite]], etc. in veins and cavities of [[basalt]]ic rocks, sometimes in [[granite]]s, [[syenite]]s, or [[gneiss]]es. It is an indicator mineral of the [[Prehnite-pumpellyite facies|prehnite-pumpellyite metamorphic facies]]. It was first discovered in [[South Africa]] by Colonel Hendrik Von Prehn, an early [[the Netherlands|Dutch]] governor of the [[Cape of Good Hope]] colony. Prehnite was the first mineral to be named after a person. ==Gallery== <gallery> Image:prehnite-pf-0001.jpg|Round cut Prehnite, 1.7 cm diameter x 1.3 cm high, 3.2 grams. Image:prehnite-pf-0002.jpg|Emerald cut Prehnite, 1.85 cm x 1.42 cm, 4.6 grams. Image:prehnite-pf-0003.jpg|Prehnite cabochon, 2.6 cm x 1.54 cm, 5.1 grams. Image:prehnite-pp-0112.jpg|Prehnite, carved pendant, 2.0 cm x 1.3 cm, 4.0 grams. Image:prehnite-pp-0134.jpg|Carved yellow Prehnite pendant, 2.4 cm x 1.8 cm, 5.5 grams. Image:prehnite-ps-0100-DV00003.jpg|Botryoidal Prehnite fragment, 12.0cm x 11.0cm, 646 grams. Image:prehnite-ps-0107-DV00018.jpg|Prehnite nodule fragment, 11.0cm x 7.0cm, 338 grams. Image:prehnite-ps-0108-DV00019.jpg|Prehnite nodule showing cleavage planes where it has separated from a cluster, 5.5cm diameter, 134 grams. Image:prehnite-ps-0116-DV00035.jpg|Prehnite nodule, 5.0cm diameter, 82 grams. Image:prehnite-ps-0128.jpg|Sliced Prehnite fragment with calcite core, 9.0 cm diameter. Image:Prehnite_HMNH1.jpg|Prehnite, New Haven Co. CT, USA Image:Prehnite09.jpg|Prehnite, Franklin, New Jersey, USA Image:Prehnite Epidpte edit.jpg|Prehnite, Epidote </gallery> ==See also== *[[List of minerals]] *[[List of minerals named after people]] ==References== *Hurlbut, Cornelius S.; Klein, Cornelis, 1985, ''Manual of Mineralogy'', 20th ed., ISBN 0-471-80580-7 ==External links== *[http://www.prehnite.com.au/specimens.html Prehnite website] [[Category:Phyllosilicates]] [[Category:Calcium minerals]] [[Category:Aluminium minerals]] [[de:Prehnit]] [[es:Prehnita]] [[it:Prehnite]] [[hu:Prehnit]] [[nl:Prehniet]] [[pl:Prehnit]] [[ru:Пренит]]