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Gemstones - formation and founding-

      Coming in countless shapes, colors and sizes, gemstones are the luxurious gifts of the earth that it offers to us. Gems form in many different environments in the Earth, and almost all gems are formed below the Earth's surface:

  • some are brought to the surface through mining
  • some are brought to the surface through earth processes (faulting, folding, large scale uplift, volcanism)

How Do Gemstones Form And Where You Should Find Them ?

  1. Formation from water near the Earth's surface

      Water near the Earth's surface interacts with minerals and dissolves them. The ability of these solutions to maintain elements in solution varies with physical conditions. If the solution conditions change (for example if the solution cools or evaporates), minerals will precipitate.

       The mineral that forms is determined by what the dissolved elements are like:

  • Silica (SiO2)-based minerals: amethyst (quartz); agate; and the formation of opal. Of these, only opal is non-crystalline (ordered blobs of gel less than a micron in diameter).
  • Copper bearing minerals: malachite and azurite; or turquoise.

      2. Hydrothermal deposits

      The formation of gems by hydrothermal processes it is similar to formation of gems from water near the Earth's surface

       The solutions involve rain water and/or water derived from cooling magma bodies. Gems crystallize from solution when it encounters open spaces such as cracks. As a result, 'veins' of minerals fill preexisting cracks.

        Minerals such as beryl (e.g., emerald), tourmaline need unusual elements, and some of these, like beryllium (for beryl) or boron (for tourmaline) are derived from cooling molten rock (magma). 

        3. Pegmatites

        Pegmatites are unusual magma bodies. As the main magma body cools, water originally present in low concentrations becomes concentrated in the molten rock because it does not get incorporated into most minerals that crystallize. Consequently, the last, uncrystallized fraction is water rich. It is also rich in other weird elements that also do not like to go into ordinary minerals. 

        The high water content of the magma makes it possible for the crystals to grow quickly, so pegmatite crystals are often large. Of course, this is important for gem specimens!

        When the pegmatite magma is rich in beryllium, crystals of beryl form. 

         If magmas are rich in boron, tourmaline will crystallize. 

         4. Magmatic gems

         Some gems crystallize in magmas or in gas bubbles (holes) in volcanic rocks. Examples include: zircon, topaz, ruby, etc.

          5. Metamorphic gems

         Metamorphic rocks are rocks changed by heat, pressure, and interaction with solutions. There are a number of types of metamorphic environments:

  • Plate tectonics creates metamorphic environments characterized by high temperature and high pressure - produce jadeite (jade). In extremely rare cases, pressures in metamorphic rocks may be high enough that diamonds form. 
  • Regionally metamorphosed rocks: large volumes of rock that are buried and changed in response to increases in pressure and temperature. Minerals found in these rocks might include gems such as garnet and cordierite.
  1. Gems formed in the mantle
  • The most abundant upper mantle mineral is olivine (peridot). Slabs of mantle material are brought to the surface through tectonic activity and volcanism.

Deep mantle gems.  Rocks such as kimberlites are erruptive volcanics that come from quite deep in the mantle and carry with them diamonds . Diamonds are made from carbon. The stable form of carbon at the Earth's surface is graphite. High pressures and temperatures are required to convert graphite to diamond. Thus, almost all diamonds formed about 100 miles below the Earth's surface. Dates suggest that their formation was restricted to in the first few billion years of Earth history.

Thank you for reading this! Thanks to everyone who made this post possible! Much love! 

Silver-Berry Team ♡

 

 

Sources: Text - https://nature.berkeley.edu/classes/eps2/wisc/Lect3.html

                Photos - https://unsplash.com/photos/0d3qxUozE-0

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