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In situ gold-bearing vein (in brown) at the Toi gold mine, Japan. In many gold mines exploited during the gold rushes of the 19th century, vein material alone was typically sought as ore material. [8] In most of today's mines, ore material is primarily composed of the veins and some component of the wall rocks which surrounds the veins. [9]
Hydrothermal vein ore deposits consist of discrete veins or groups of closely spaced veins. Veins are believed to be precipitated by hydrothermal solutions travelling along discontinuities in a rockmass. [10] They are commonly epithermal in origin, that is to say they form at relatively high crustal levels and moderate to low temperatures.
"Mining on the Comstock", depicts the headframes and mills of the various mines, and the mining technology used at Comstock, most prominently the method of square-set timbering developed there to work the veins. Comstock Lode geologic map, north. Ophir is in the top center; "qz" is quartz and signifies the Comstock Lode. [1]:
The Guanajuato Mining District, Mexico: This district has been mined for centuries and is known for its high-grade epithermal veins containing gold and silver. [11] The Baguio Mineral District, Philippines: This district is home to numerous epithermal vein deposits, including the Acupan Mine, one of the largest gold mines in the Philippines. [12]
Along an ore shoot, there is a rich gathering of different minerals within a vein. The veins can resemble a pipe, chimney or ribbon in structure and are displaced mainly vertically oriented but also can be horizontal with large veins extending approximately 30 m (100 ft) horizontally and 150 m (500 ft) vertically. [3]
The zone contains hundreds of mines and prospects, including some of the best-known historic mines of the gold-rush era. Individual gold deposits within the Mother Lode are gold-bearing quartz veins up to 15 metres (49 ft) thick and a few thousand feet long. The California Mother Lode was one of the most productive gold-producing districts in ...
Quartz is generally the dominant mineral in the veins, but there are also gold bearing carbonate dominant veins in orogenic deposits. [15] Ore bodies of orogenic gold deposits are generally defined by ≤ 3–5% sulfide minerals, most commonly arsenopyrite in metasedimentary host rocks and pyrite /pyrrhotite in meta-igneous rocks, and ≤ 5 ...
Drift is a more general mining term, meaning a near-horizontal passageway in a mine, following the bed (of coal, for instance) or vein of ore. A drift may or may not intersect the ground surface. [3] A drift follows the vein, as distinguished from a crosscut that intersects it, or a level or gallery, which may do either. [4]