- المجال: Mining
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The U.S. Bureau of Mines (USBM) was the primary United States Government agency conducting scientific research and disseminating information on the extraction, processing, use, and conservation of mineral resources.
Founded on May 16, 1910, through the Organic Act (Public Law 179), USBM's missions ...
A mineral group including fayalite, Fe<sub>2</sub>SiO<sub>4</sub>; forsterite, Mg<sub>2</sub>SiO<sub>4</sub>; liebenbergite, (Ni,Mg)<sub>2</sub>SiO<sub>4</sub>; and tephroite, Mn<sub>2</sub>SiO<sub>4</sub>; orthorhombic; olive green, grayish green, brown, or black; members intermediate in the forsterite-fayalite crystal solution series are common rock-forming minerals in gabbros, basalts, peridotites, and dunites; alters hydrothermally to serpentine. Fayalite occurs in some granites and syenites, forsterite in thermally metamorphosed dolomites, and tephroite in iron manganese ore deposits and their associated skarns.
Industry:Mining
A mineral group, 2(KFCa<sub>4</sub>(Si<sub>8</sub>O<sub>20</sub>).8H<sub>2</sub>O) (fluorapophyllite) with F replaced by (OH) (hydroxyapophyllite) and K replaced by Na (natroapophyllite); occurs in square micaceous crystals as secondary minerals in cavities in igneous rocks.
Industry:Mining
A mineral group, 2(KFCa<sub>4</sub>(Si<sub>8</sub>O<sub>20</sub>).8H<sub>2</sub>O) (fluorapophyllite) with F replaced by (OH) (hydroxyapophyllite) and K replaced by Na (natroapophyllite); occurs in square micaceous crystals as secondary minerals in cavities in igneous rocks.
Industry:Mining
A mineral group; characterized by double chains of silica tetrahedra having the composition A<sub>0-1</sub>B<sub>2</sub>Y<sub>5</sub>Z<sub>8</sub>O<sub>22</sub>(OH,F,Cl) , where (A=Ca,Na,K,Pb,B), (B=Ca,Fe,Li,Mg,Mn,Na), (Y=Al,Cr,Fe,Mg,Mn,Ti), and (Z=Al,Be,Si,Ti); in the orthorhombic or monoclinic crystal systems, including actinolite, anthophyllite, arfvedsonite, cummingtonite, hornblende, richterite, glaucophane, grunerite, anthophyllite, riebeckite, tremolite, and others. All display a diagnostic prismatic cleavage in two directions parallel to crystal faces and intersecting at angles of about 54 degrees and 124 degrees . Some members may be asbestiform.
Industry:Mining
A mineral having economic value as a coloring agent. The most important are the red and yellow ochers and brown sienna, which consists of iron oxides with some impurities, and the brown umbers in which manganese oxide is also present. When the iron-oxide content is high the term oxide is used in preference to ocher.
Industry:Mining
A mineral having large interstices in its structure may accommodate various foreign ions in these holes; such a mineral is then said to be stuffed. The stuffing may have considerable consequences on the stability of the mineral.
Industry:Mining
A mineral in the olivine series composed of 70% to 90% fayalite and 30% to 10% forsterite.
Industry:Mining
A mineral in treelike or mosslike forms; e.g., manganese oxide.
Industry:Mining
A mineral in which sulfur and antimony are united chemically with a metal.
Industry:Mining
