THE GLORY OF BLUE
GEM (ORNAMENTAL MINERAL OR ORGANIC SUBSTANCE)
Gem, commonly, a mineral or organic substance, cut and polished and used as an ornament. Gems also are used as seals (items of assurance) and as talismans (good-luck charms). For birthstones, see month.
PRECIOUS AND SEMI PRECIOUS GEMSTONES: MYTH AND REALITY
The idea that some gemstones are precious and others are only semi-precious is familiar to every buyer of colored stones. Precious stones - diamond, ruby, sapphire and emerald - traditionally command high prices due to their extraordinary color or brilliance and extreme rarity.
While the precious stones are deservedly famous, the conventional distinction between precious and semi-precious gems is laden with myth and misconceptions. Let's try to sort out some of the myths from the reality.
One common misconception is that the distinction between precious and semi-precious gemstones is traditional, going back many centuries. In fact it is a recent innovation, dating only to the nineteenth century. The first use of "semi-precious" to mean "of less commercial value than a precious stone" can be traced back to only 1858.