What is Jade? Jade can be described as a mineral useful as jewelry or ornaments. It is a mineral with a monoclinic crystal system. This material mostly has a green color, but it can appear in virtually all colors. It has a crystal habit of intergrown grainy or fine fibrous aggregate type. Its fractuRead more
What is Jade?
Jade can be described as a mineral useful as jewelry or ornaments. It is a mineral with a monoclinic crystal system. This material mostly has a green color, but it can appear in virtually all colors. It has a crystal habit of intergrown grainy or fine fibrous aggregate type. Its fracture is splintery, and it is a brittle material. The hardness can be given as 6 – 7 on the Mohs scale. Jade is a translucent material with a specific gravity of 2.9 – 3.38.
There are two forms of jade; they are nephrite jade and jadeite jade. Until 1863, it was difficult to determine whether jade was nephrite or jadeite. Nephrite contains a microcrystalline interlocking matrix with a fibrous appearance made of calcium, magnesium-iron rich amphibole minerals. It becomes more green in color when the iron content grows higher. On the other hand, jadeite is rich in sodium and aluminum pyroxene. It is the most precious type of jade and has a microcrystalline structure with an interlocking growth of crystals. This type of jade can be found only on metamorphic rocks.
There are many ornamental uses of jade in East Asia, South Asia, and Southeast Asia art. It is also a precious material in Latin America, including Mexico and Guatemala.
What is Serpentine?
Serpentine is a subgroup of kaolinite-serpentine, which has greenish, brownish, spotted minerals that exist in serpentinite rocks. This type of material is useful as a source of magnesium and asbestos. It is also useful as a decorative stone. The name serpentine comes from the green color it has, which resembles a serpent.
This subgroup of this mineral has rock-forming hydrous magnesium iron phyllosilicate minerals. These minerals are a result of the metamorphism of ultramafic rocks. Moreover, there can be some other elements, such as chromium, manganese, cobalt, and nickel. Moreover, this subgroup has polymorphous minerals, which means there is the same chemical formula with different atomic structures.
The precious or noble forms of serpentine are more attractive and durable forms, and these are useful extensively as gems and used in ornamental carvings. Furthermore, it can be easily carved, polished excellently, and has a pleasingly greasy feeling. There are, however, less valuable serpentine ores with various hardnesses and clarities that are sometimes dyed to imitate jade.
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Magmatic Sulfides and Cumulates Mafic and ultramafic magmas, like all common magmas, contain the major elements oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium. But they typically also contain other elements including sulfur, nickel, and less common metals such as platinumRead more
Magmatic Sulfides and Cumulates
Mafic and ultramafic magmas, like all common magmas, contain the major elements oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium.
But they typically also contain other elements including sulfur, nickel, and less common metals such as platinum, palladium, and chromium.
As these magmas cool and crystallize, the first minerals to form are plagioclase, pyroxene, and olivine – all made of major elements.
Consequently, the concentrations of sulfur and other minor elements increase in remaining melt.
Eventually, sulfur concentration becomes great enough so that sulfide minerals begin to crystallize.
The sulfide minerals, typically containing iron and nickel, may also contain relatively high concentrations of platinum, palladium, and other minor metals.
Sulfides have greater densities than silicate minerals and the mafic or ultramafic melts.
So, the denser sulfide minerals will, over time, begin to sink. Eventually, after more cooling and crystallization, significant deposits of sulfide minerals may accumulate on the bottom of a magma chamber.
The deposits, which may form centimeters-, or meters-thick layer called a cumulate, are often entirely, or nearly entirely, composed of sulfide minerals.
This process produces magmatic sulfide deposits, which are the most important sources of platinum, palladium, chromium, and several other metals.
Cumulate sulfide minerals include pentlandite (Fe,Ni)9S8, chalcopyrite (CuFeS2), pyrrhotite (Fe1-xS), and pyrite (FeS2)
Cumulate sulfide deposits account for almost 60% of the world’s nickel production and more than 95% of platinum and palladium production.
These deposits are associated with mafic and ultramafic magmas but not, generally, with felsic magmas, because felsic magmas are so viscous that they cool and crystallize before dense minerals can settle.
Sulfides are not the only kind of mineral that can become concentrated in a cumulate deposit.
Oxides – including magnetite (Fe3O4), ilmenite (FeTiO3), and chromite (FeCr2O4) – may settle and collect at the bottom of a magma chamber, too.
These chromite cumulates produce not only significant amounts of chrome, but also very large amounts of platinum, palladium, and related elements.
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