Main index --- Minerals list --- Jewelry index --- Hardness index Sapphire Ruby
Name:Corundum - Ruby and Sapphire
Derivation: From "kurundum" (Tamil)
From "rubeus" (Latin) red
From "sappheiros" (Greek) lapis lazuli
Formula: Al2O3
Description: Very hard crystal. Red corundum is ruby (left). Blue curundum is sapphire (right). Or you can just have corundum (below right).

Corundum Corundum is a very hard stone. Another name of Corundum is Emery, and Emery paper is used for rubbing things smooth.

Sapphire Sapphire was originally the name of lapis lazuli. The name of sapphire was Hyacinthus, because they were supposed to look like the flower. Now Hyacinthus is another name of zircon (which looks nothing like sapphire!) Romans used Sapphires for the development of greater trade with India at the time of the Emperor Trajan.

Ruby was used for different types of red stones. It was fixed as Red Corundum in about 1800. In the Bible (King James' version), in Proverbs, it says "Who can find a virtuous woman? For her price is far above Rubies." However, it is now thought that Coral was meant by this. You can see from this, and the muddle over Sapphire's name, that there has been great confusion over the names of stones throughout history.

Good quality rubies are still very valuable, as much or more than diamonds. The "perfect ruby" is an alchemist term for the Elixir or Philosopher's Stone, which would turn ordinary metal to gold, and would make you live for ever. (No-one ever found it! But alchemists learn a lot about chemicals while trying, and provided a foundation for modern chemistry). Some rubies can be cut so there are pale streaks coming from a point. These are called star rubies.

Larger pictures of Corundum:

Red corundum is Ruby. These two crystals are opaque and have poor colour (good quality crystals of ruby would be extremely expensive).

Ruby Ruby

This is a (very small) cut ruby.


This is a star ruby (not good quality). You can just see a paler line or two across it.


Natural ruby (the red bit).


Blue corundum is Sapphire. This crystals is opaque and has poor colour (good quality crystals of sapphires would also be expensive).


Natural sapphire (also opaque and poor colour).

Sapphire Sapphire

This is an opaque hexagomal crystal of corundum.