Ruby and blue, green, pink and yellow sapphires all belong to the same corundum family. Corundum has hardness of nine in Moh's scale and specific gravity around four.These are the hardest gemstones but diamonds and one of the heaviest too. Corundum contains aluminum and oxygen. Natural corundum is opaque but some times it reacts with water in the mines and takes a crystalline form. This crystaline structure converts it into gemstones. When this corundum comes into contact with coloring agents likes of chromium, nickel etc (in a very small quantity) and reacts chemically inside the mines, it converts  naturally into Ruby or Pink-blue-yellow or green Sapphires.

The best quality ruby and blue-yellow sapphires are found in Burma (Myanmar). Burmese stuff are beautiful and bright in color. Good quality Burmese are transparent. Burmese rubies are rare and fetch high value. A 5 carats fine ruby may go up to $ 40 to 60 thousands per carat. Burmese sapphires are also expensive.

Cambodian, Vietnam And Kabul rubies some times resemble with Burmese.

Rubies and sapphires found in Ceylon are generally transparent but not having the rich color as Burmese. Ceylon produces very good quality of pink saphire.

Thai rubies and sapphires normally have a black tint due to presence of iron. They are rich in color, and have very hard textures. Thai rubies and sapphires also have good lusture.

African and Indian rubies are of inferior quality and generally opaque or translucent. Generally those are treated as corundum and not ruby. Kenya, Madagascar are rich sources of commercial ruby. Koromoro, Johnson and Best pockets are other African varieties. Best pocket mines produce very nice quality, an exception in African mines. Johnson is also good one.

Tanzania has recently started producing very good quality of ruby. Some pieces are extra fine and resembles Burmese quality.

Rubies ( corundum) are also found plenty in Orissa, Bastar, Mysore and Andhra regions of India. Normally Indian and African rubies are used for making beads, drops and cabs.These qualities are not very good for cut-stones. Most of these stones are cut and polished in Jaipur, the pink city of India.

The best quality rubies are found in Burma but the blue sapphires are mined from Kashmir (India).These are the rare of the rarest gemstones. These transparent stones have a peacock blue color with great lustre. A pin-point color tint in the bottom of a cut stone spreads to the whole stone giving it a marvelous look.

Some foreign materials are found naturally in rubies and sapphires of some origins. These materials embedded with in colloidal state, gives these stones milky look. This milky inclusions converts into a star like six lined shape in some of the stones and those are called star rubies or sapphires. Stars are costlier than the normal rubies and sapphires because of its rarity and beauty. Americans, Europeans and Japanese people love star rubies and sapphires very much.