A semi-precious stone is a natural gem, mined from the earth. The difference between precious and semi-precious stones are the availability and quality. Although rubies, emeralds and diamonds, among others, are considered precious gemstones, they can be categorised as semi-precious if the quality is lower.
Amethyst is a purple toned, semi-precious stone that comes from the mineral quartz. The addition of iron to the other properties in quartz produces the beautiful colour.
This semi-precious stone can be found in blue, green and red. It is mined in other places, but the most well known in the American Southwest, where Native Americans have used it for thousands of years.
Topaz is most commonly found in a honey colour. It is also naturally found in blue, orange, red, green and violet. Pink topaz is sometimes created by heating this very hard stone.
This green semi-precious stone is called the "evening emerald" or the "volcanic gemstone." It is also known as olivine, and comes in many shades of green.
Most common opals have a translucent, milky quality to them. Fire opals, containing black backgrounds, are mined in Australia.