Both ruby and sapphire belong to the corundum-group and are made of trigonally crystallized aluminium-oxyde (Al₂O₃). Due to its  hardness (9) and its high refractive index, the mineral specimens of corundum, e.g. ruby, sapphire and padparadscha are very longing.  Aso very rare are the star-rubys and star-sapphires, which show asterism due to geometrical structured rutile-inclusions. All gems with all other colours are called sapphires (except red, because they are called rubys) .The most longing colour of  sapphire is a dark corn-flower-blue, the most longing colour for rubys is a dark blood-red.
Rubys occure in or near rivers of  Tanzania, Burma, Sri Lanka und Thailand, sapphires are discovered in Thailand, Burma and Sri Lanka, also  Montana and Australia are known to deliver sapphires.

The different colours of ruby and sapphire are also named after their occurances in the trade:
 

 Ruby: 

Sri-Lanka-ruby --- weak red
Thailand-ruby  ----lightly brownish red
Burma-ruby -------lightly blueish red
 
 Sapphire: 
Sri-Lanka-sapphire ------- weak blue
Thailand-sapphire --------- silky blue
Montana-sapphire --------- steel blue
Australia-sapphire --------dark, inky blue
 
Padparadscha:   Orange
 Colourless Sapphire: