How are diamonds and other valuable stones formed naturally?

Answer 1

heat and pressure

The conditions required for diamond formation in the lithospheric mantle require considerable depth. The range of depth required for diamond formation is calculated to be between 90–120 miles (140–190 kilometers)[10][6] The rate at which temperature changes with increasing depth into the Earth varies greatly in different parts of the Earth. In particular, under oceanic plates the temperature rises more quickly with depth, beyond the range required for diamond formation at the depth required.[10] The correct combination of temperature and pressure is only found in the thick, ancient, and stable parts of continental plates where regions of lithosphere known as cratons exist.[10] Long residence in the cratonic lithosphere allows diamond crystals to grow larger.

Through studies of carbon isotope ratios (similar to the methodology used in carbon dating, except with the stable isotopes C-12 and C-13), it has been shown that the carbon found in diamonds comes from both inorganic and organic sources. Some diamonds, known as harzburgitic, are formed from inorganic carbon originally found deep in the Earth's mantle. In contrast, eclogitic diamonds contain organic carbon from organic detritus that has been pushed down from the surface of the Earth's crust through subduction (see plate tectonics) before transforming into diamond.[6] These two different source carbons have measurably different 13C:12C ratios. Diamonds that have come to the Earth's surface are generally very old, ranging from under 1 billion to 3.3 billion years old.

Diamonds occur most often as euhedral or rounded octahedra and twinned octahedra known as macles or maccles. As diamond's crystal structure has a cubic arrangement of the atoms, they have many facets that belong to a cube, octahedron, rhombicosidodecahedron, tetrakis hexahedron or disdyakis dodecahedron. The crystals can have rounded off and unexpressive edges and can be elongated. Sometimes they are found grown together or form double "twinned" crystals grown together at the surfaces of the octahedron. This is all due to the conditions in which they form. Diamonds (especially those with rounded crystal faces) are commonly found coated in nyf, an opaque gum-like skin.

Answer 2

Diamonds are formed when carbon is subjected to great pressure usually 90-120 miles beneath the surface of the earth.

Diamonds get to the surface when they are pushed up along with magma in a volcano.

The US is host to a quite nice diamond pipe in Arkansas called "Crater of Diamonds State Park" if you want to go dig some up yourself.

I just learned from Wikipedia that micro-diamonds can occur at meteor strikes.

Other precious stones are formed similarly, through pressure or heat; but not at such extremes as diamonds. The chemical composition of the material determines what sort of gem stone it will become. Emeralds are aluminium cyclosilicate, Rubies and Saphires are aluminum oxides. Additional elements provide the varying colors of these stones.

Answer 3

Well in the case with diamonds, its just pressure and time. Diamonds are nearly pure carbon.

As for other precious and semiprecious stones, thereis also heat and pressure, and they crystallize as molten minerals or rocks cool or sometimes certain ones can be found in hydrothermal areas where water evaporates and crystals are left behind.

Answer 4

Okay, so first you take a pile of coal (carbonates specifically, I think) And you put it down in the Earth's crust, and you compress it for a couple hundred millennium. This pressure, and subsequent heat, changes the coal/carbons into a diamond.

Answer 5

Previous answers are great, except coal is not a carbonate, even though it is made from carbon. Carbonates have the basic chemical formula of CaCO2 .

Other sources for gemstones include metamorphic rocks (ex. garnet) and pegmatites, which are areas of igneous rocks with large deposits of minerals containing rare elements (ex. sapphires & rubies).

Answer 6

Exactly as they are made now artificially : carbon, trace elements, heat and pressure.

Answer 7

Do I look like a minor. GOsh!