With gemstones, the richer and purer the color, the more valuable the stone becomes. As a gemstone becomes larger, while maintaining a rich and pure color, it becomes progressively more rare and thereby more expensive.
Gemstones can be set in any type of jewelry and can also be used in engagement rings. The hardness level of a gemstone will affect the practical use of the stone in jewelry. For example, rubies and sapphires are more practical for engagement rings since they are quite hard and therefore are better suited or everyday wear on the hand. Softer gemstones are more prone to being damaged if subjected to certain impact.
There is a common distinction between precious gemstones and semi-precious gemstones, which began during the mid-1800s and has become more prevalent over the years; the precious stones being Ruby, Sapphire, and Emerald, while the semi-precious stones comprising pretty much all else.
As the term denotes, the precious stones are generally more rare, more prized, and more valuable. However, this does not mean that semi-precious stones are not beautiful and valuable in their own right. In fact, there may be instances in which a semi-precious stone could be more rare and more valuable than a precious stone. An example is Alexandrite, which can be as expensive as a fine Ruby or Sapphire.