Learning about mineral crystallization and the geological processes involved in gem formation will help gemologists understand some of the properties they ll encounter in gemstones. How gemstones are formed minerals form under various conditions in the earth. Only two gemstone varieties diamond and peridot form in the earth s mantle which represents 80 of the earth s volume. Diamonds are not only formed under the heat and pressure of the earth s gravity but can form in the midst of a collision between earth and an asteroid. Metamorphic as the name suggests these are gems.
Generally speaking there are 4 ways gemstones can form. Diamonds created during a cosmic collision are not likely to be of gemstone quality. Most form as crystals solids whose atoms are arranged in highly ordered repeating patterns called crystal systems. Russia claims to have a deposit of diamonds resulting from a collision 35 million years ago. Diamond is a solid form of pure carbon with its atoms arranged in a crystal.
Precious gems are formed in different ways and composed of different materials meaning their appearances vary vastly. Igneous these minerals are created deep within the earth diamonds ruby sapphire peridot hydrothermal similar to the rock candy example gemstones are formed when bodies of mineral rich water cool. Solid carbon comes in different forms known as allotropes depending on the type of chemical bond. The top layer of the earth with a depth of 3 to 25 miles. This is when minerals are forced together under great pressure and heat usually by tectonic plates moving underneath each other.
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Diamonds made of carbon atoms are the hardest natural substance found on. Most gemstones form in the earth s crust. The two most common allotropes of pure carbon are diamond and graphite in graphite the bonds are sp 2 orbital hybrids and the atoms form in planes with each bound to three nearest neighbors 120 degrees apart. Sometimes diamonds are formed when parts of the earth s crust are subducted one plate is dragged beneath another when they collide due to composition and density differences. The earth s upper mantle is a layer 100 miles 160 km deep in the earth which separates the surface from the molten core.The majority of gemstones are formed by metamorphism. The majority of gemstones are formed by metamorphism. Diamonds made of carbon atoms are the hardest natural substance found on. Precious gems are formed in different ways and composed of different materials meaning their appearances vary vastly. Generally speaking there are 4 ways gemstones can form.
The earth s upper mantle is a layer 100 miles 160 km deep in the earth which separates the surface from the molten core. Learning about mineral crystallization and the geological processes involved in gem formation will help gemologists understand some of the properties they ll encounter in gemstones.
