Phenacite or phenakite is a nesosilicate mineral consisting of beryllium orthosilicate, Be₂SiO₄. Occasionally used as a gemstone, Phenacite occurs as isolated crystals, which are rhombohedral with parallel-faced hemihedrism, and are either lenticular or prismatic in habit: the lenticular habit is determined by the development of faces of several obtuse rhombohedra and the absence of prism faces. There is no cleavage, and the fracture is conchoidal. The hardness is high, being 7.5 - 8; the specific gravity is 2.96. The crystals are sometimes perfectly colorless and transparent, but more often they are greyish or yellowish and only translucent; occasionally they are pale rose-red. In general appearance the mineral is not unlike quartz, for which indeed it has been mistaken. The silicate minerals make up the the largest and most important class of rock-forming minerals. ... Minerals are natural compounds formed through geological processes. ... General Name, Symbol, Number Beryllium, Be, 4 Series Alkaline earth metals Group, Period, Block 2 (IIA), 2, s Density, Hardness 1848 kg/m3, 5. ... A gemstone is a mineral, rock (as in lapis lazuli) or petrified material that when cut or faceted and polished is collectible or can be used in jewellery. ... 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. ... In materials science, hardness is the characteristic of a solid material expressing its resistance to permament deformation. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... For other uses of this word, see Quartz (disambiguation). ...

Phenacite is found in high-temperature pegmatite veins and in mica-schists associated with quartz, chrysoberyl, apatite and topaz. It has long been known from the emerald and chrysoberyl mine on the Takovaya stream, near Ekaterinburg in the Urals of Russia, where large crystals occur in mica-schist. It is also found with topaz and amazon-stone in the granite of the Ilmen mountains in the southern Urals and of the Pikes Peak region in Colorado (USA). Large crystals of prismatic habit have more recently been found in a feldspar quarry at Kragero in Norway. Framont near Schirmeck in Alsace is another well-known locality. Still larger crystals, measuring 1 to 2 in. in diameter and weighing 28 lb. have been found at Greenwood in Maine, but these are pseudomorphs of quartz after phenacite. rock with mica Mica sheet mica flakes The mica group of minerals includes several closely related materials having highly perfect basal cleavage. ... Categories: Mineral stubs | Metamorphic rocks ... The mineral or gemstone chrysoberyl, not to be confused with beryl, is an aluminate of beryllium with the formula BeAl2O4. ... Apatite is a group of minerals, usually referring to: hydroxylapatite, fluorapatite, and chlorapatite, named for high concentrations of OH-, F-, or Cl- ions, respectively, in the crystal lattice. ... This article is about the mineral or gemstone, for other uses see: Topaz (disambiguation). ... For other things of this name, see Emerald (disambiguation). ... Photograph of snow-covered Yekaterinburg Yekaterinburgs Church on the Blood, built on the spot where the Tsar and his family were murdered. ... The Ural Mountains, (Russian: Ура́льские го́ры = Ура́л) also known simply as the Urals, are a mountain range that run roughly north and south through western Russia. ... Granite - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... Pikes Peak (formerly Pikes Peak, see below) is a mountain in the Front Range of the Rocky Mountains, near Colorado Springs, Colorado. ... This is the article on the state. ... Feldspar (from the German Feld, field, and Spat, a rock that does not contain ore) is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earths crust. ... Capital Strasbourg Area 8,280 km² Regional President Adrien Zeller Population  - 2004 estimate  - 1999 census  - Density 1,793,000 1,734,145 209/km² Arrondissements 13 Cantons 75 Communes 903 Départements Bas-Rhin Haut-Rhin Alsace (French: Alsace; Alsatian/German: Elsaß) is a région of France. ... State nickname: The Pine Tree State Other U.S. States Capital Augusta Largest city Portland Governor John Baldacci Official languages None Area 86,542 km² (39th)  - Land 80,005 km²  - Water 11,724 km² (13. ...

For gem purposes the stone is cut in the brilliant form, of which there are two fine examples, weighing 34 and 43 carats (6.8 and 8.6 g), in the British Museum. The indices of refraction are higher than those of quartz, beryl or topaz; a faceted phenacite is consequently rather brilliant and may sometimes be mistaken for diamond. The main entrance to the British Museum The British Museum is one of the worlds greatest and most famous museums. ... This article is about the mineral, for the rifle see Beryl assault rifle. ... A scattering of round-brilliant cut diamonds shows off the many reflecting facets. ...

This article incorporates text from the public domain 1911 Encyclopædia Britannica. The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ... The Eleventh Edition of the Encyclopædia Britannica ( 1911) in many ways represents the sum of knowledge at the beginning of the 20th century. ...