Unlike gold, diamonds are verymuch native to the earth. while gold is supposed to have come from outerspace, diamonds are formed on the earth. Dimonds are pure corbon converted in crystal lattice by very high temperature and pressure inside earths mantle. It is assumed that they have formed 150 to 250 kilometers depths and have surfaced during volcanic eruption. Diamond are found in all colors like in a Rainbow. Traces of impurities or effects is lattice structure give them colorful appearance. Most common are crystal clear diamond (no impurity) orange to brown (nitrogen), blue (Boron), diamond weight is measured in carats (200 ml grams) Diamond prices depends on Clarity, Color and Carats. Pink and Red diamonds are considered very rare and priced high.
Ruby and Emerald are other popular precious stones. There are great differences in physical and chemical property of Ruby and red diamond or Emerald and green diamond. On the Mho scale diamond is hardest then Ruby and then Emerald. Diamond is crystalize structure of pure Carbon. Both Ruby and Emerald are also formed due to high pressure and high temperature inside earth. Ruby is mainly Aluminum, Oxygen, corundum and minor traces of other elements.
Emerald is a type of beryl and includes beryllium and traces of other minerals. Unlike diamond both Ruby and emerald have internal crystalline defects and never equal diamond in clarity and homogenous structure.
Out of the nine major precious stones attributed to planets, seven are found in earth crust. They are Diamonds, Ruby, Emeralds, Sapphires, Agate and Cats Eyes. Rest of the two are found in the high seas. They are not real stones but are objects made by living creatures. Coral is the fungi, which builds reeves in seas. Over the centuries the coral reeves get solid and formed red coral stone.
Pearl is an excretion of an insects in a sea shell. Sea shells under certain temperature and depth conditions can create such beautiful objects. It is said that if oyster is impregnated by octopus poison, a rear black pearl is created.