GemstonesFinishingBirthstoneGem galleryJewelry
 

 Formation

Source

Natural inclusions

Chemical process

Faceting

Polishing

Imitaion

 

HOW ARE GEMSTONES FORMED

Most gemstones are mineral crystals that formed during one of three rock making processes: igneous rocks, metamorphic rocks and sedimentary rocks. Gemstones that have a mineral origin are found in rocks, or in gem gravels derived from these rocks. Rocks them­selves are made up of one or more minerals, and may be divided into three main types. The formation of these three types -igneous, sedimentary, or metamorphic - is a continuous process, best described in terms of the rock cycle. Gem-quality minerals with­in these rocks may be easily accessible at the Earth's surface, or lie buried deep beneath it. Others, separated from their host rock by erosion, are carried by rivers to lakes or the sea.

 
IGNEOUS ROCKS
Deep within the earth's inferno is a stew of molten rock and gases, called magma. As magma wells up within the earth, intense pressure builds forcing the liquid rock toward the surface, sometimes breaking through to be known as lava. It slowly cools forming igneous rocks, and within these rocks and gas bubble spaces, interlocking crystals grow. The minerals present, the cooling time and the environment will all play a role in the way these crystals form. Examples of gemstones found in igneous rock: diamonds, topaz, kunzite and spinel.
 
METAMORPHIC ROCKS
Lastly, intense pressure and high temperatures can actually recrystallize, transforming the composition of the rock. This can happen deep within the earth's crust and it can also happen with direct contact with hot magma. Emerald sometimes also forms in hydrothermals associated with magma. Other examples of metamorphic gemstones include sapphire, jadeite and peridot.
 
SEDIMENTARY ROCKS
Rock fragments near the earth's surface are often washed into riverbeds and seabeds. Over time, layers of rock fragments, mud and other organic and non-organic elements are compacted together in hard rock. Sometimes sea creatures, bugs or other organic elements will get trapped within the rock formations. Examples of sedimentary rocks include limestone, shale and sandstone. In addition, most gemstones are found in sedimentary deposits. Discovered in riverbeds, these alluvial deposits include metamorphic gems such as sapphire and ruby.
 
ORGANIC GEMS
Organic gems come from plants and animals. Natural pearls form around foreign bodies that have made their way inside the shells of marine or freshwater shellfish. Cultured pearls are produced artificially in large fisheries, many in the shallow waters off the shores of Japan and China. Shells treated as gems may come from animals as diverse as snails and turtles, living in the ocean, in fresh water, or on land. Coral is made up of the skeletons of tiny marine animals called coral polyps. Bone, or ivory from the teeth or tusks of mammals, may come from recently living animals or from fossils thousands of years old. Amber is fossilized tree resin, collected from soft sediments or the sea. Jet is fossilized wood, found in some sedimentary rocks.

  Natural Gemstones

 


 

   
The Rainforest Site
Custom Search

Home Finishing Birthstones Gallery Jewelry Contact us