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Geodes

Geodes.

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Geodes

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  1. Geodes Geodes, a term derived from a Greek word meaning earth-shaped, are irregular, roughly spherical bodies. They can be oblong or shaped like invertebrate fossils. Some are hollow and lined with most beautiful and unusual layers and clusters of various mineral crystals, but others are completely filled by inward-growing crystals.Hollow geodes, relatively lightweight compared with those completely filled, are more desirable because they generally contain a greater variety of minerals that have grown well formed crystals. http://www.isgs.uiuc.edu/servs/ pubs/geobits-pub/geobit3/ geobit3.html

  2. How geodes form Geologists have proposed several theories to explain the conditions and processes that form geodes, but none seems to be entirely adequate to explain all geode features.

  3. Gypsum-anhydrite protogeode in the Harrodsburg equivalent along Highway 313 near Fort Knox, Kentucky. http://www.indiana.edu/~xl10rd/indianageode.htm

  4. Weathered protogeodes in the Harrodsburg equivelent. These protogeodes originally were filled with gypsum.

  5. Beryl Gem Pocket

  6. WHERE DO GEMS FORM AND WHERE ARE THEY FOUND ? http://www.geology.wisc.edu/~jill/Lect3.html

  7. Magmatic gemstones

  8. Diamonds form under remarkable conditions! The temperatures are about 900 - 1300 C in the part of the Earth's mantle where diamonds form The pressure is between 45 - 60 kilobars (kB) 50 kB = 150 km = 90 miles below the surface 60 kB = 200 km = 120 miles below the surface

  9. Diamonds are carried to the surface by volcanic eruptions. The volcanic magma conduit is known as a kimberlite pipe or diamond pipe. We find diamonds as inclusions in the (rather ordinary looking) volcanic rock known as kimberlite. NOTE: The kimberlite magmas that carry diamonds to the surface are often much younger than the diamonds they transport (the kimberlite magma simply acts as a conveyer belt!).

  10. To ensure they are not converted to graphite, diamonds must be transported extremely rapidly to the Earth's surface. It is probable that kimberlite lavas carrying diamonds erupt at between 10 and 30 km/hour (Eggler, 1989). Within the last few kilometers, the eruption velocity probably increases to several hundred km/hr (supersonic!).

  11. Metamorphic gemstones

  12. Alluvial Gemstones

  13. Formation from water near the Earth's surface

  14. Formation of gemstones by hydrothermal and pegmatitic processes

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