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| | | | Every investor in the mining industry has heard about porphyry deposits, yet few have a real understanding of what that term signifies. Many investors appreciate that porphyry deposits are often enormous in size and represent the most important source of copper and one of the leading sources of gold. In fact, the single largest supplier of gold in the world, with 2.5 million ounces of annual production, is the enormous Grasberg gold-copper mine in Indonesia, which is based on a porphyry deposit. | | |
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| | | | Separating the metal- bearing minerals from the barren rock ("gangue") is typically the most capital intensive part of the whole mining process and is also the most expensive to operate. Often, the effectiveness of the metal recovery part of the mining process (of which crushing and grinding is a major component) is the main determinant of whether or not a mine will be a profitable undertaking. | | |
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| | | | People without a geological background are often surprised to learn that most gold deposits are created by gold that is carried in solutions. Most people think of gold as being nearly impermeable to even the strongest acids. However, water will dissolve gold quite readily when it is heated to about 250 degrees centigrade and kept in a liquid state by subjecting it to immense pressure deep in the crust, with a little sulfur, chlorine and the like added to the mix. | | |
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| | | | Induced polarization, or IP, surveys, are a common geophysical technique used to detect the presence of metal in the ground. The technique involves the laying of a wire loop on the ground, typically in a square shape of 50 to 150 meters to a side. | | |
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| | | | The metal in most ore bodies occurs in the form of metal-bearing minerals. That is, the metal is usually bound up with other elements in sometimes complex chemical compounds. The most common of the secondary elements is sulfur. Other common elements in metallic minerals include arsenic, antimony, tellurium and other metals such as iron. | | |
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| | | | Most of the platinum group metals produced each year are mined from mafic or ultra-mafic intrusive complexes. These terms, in the simplest way, refer to masses of rock that originated as metal-rich molten rock or "magma". The metals in the magma were derived from the base of the earth's crust, or beneath the crust, effectively tapping the metal-rich core of the earth. | | |
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