Ruby: The First King of Gems. Ruby is the red variety of corundum, the hardest substance on the Mohs scale, with a rating of It is the combination of hardness and rich color that make fine rubies so valuable.
The range of colours shown by fluorite is equaled by few other gemstones. It may occur in beautiful cubic crystals or as a massive crystalline variety displaying banded or radiating patterns. Although the stone is somewhat soft for use as a normal.