Chalcedony

A crypto-crystalline sub-species of quartz. It is generally of a milky brown colour, but there are also rarer blue (blue chalcedony), green (chrysoprase) and orange-red (cornelian) varieties. Very occasionally it may be transparent.

Agate is frequently stained to resemble types of chalcedony; so particular care should be taken when buying chalcedony that you are not, in fact, about to be sold an imitation.

The mineral is found in Madagascar, Brazil, India, China and the USA.

Apatite

Apatite is a naturally occurring gemstone. It is basically known for its asparagus green color but it is found in wide range of colors, from colorless to pink, yellow, blue to violet. The best apatite is neon greenish blue with a clean clarity. The cost of the stone increases with the intensity of the color.

Apatite's property is fairly soft and is rarely used for rings, but is very popular as earrings and pendants because of its unusual intense green color. The hardness of the stone is 5 to 6.5 on Moh's scale. It has a vitreous luster and is sensitive to acids.

The name, 'apatite' has been taken from a Greek word 'apate,' which mean to deceive. It is so named because one can be easily get confused with variety of other stones like tourmaline, peridot and beryl.

Apatite is found in Burma, Brazil, India, Madagascar, Kenya, Mexico, Norway, Sri Lanka, South Africa, and the United States.

Apatite is found in all igneous, sedimentary and metamorphic rocks. It can also be cut as gems but the softness of apatite prevents its acceptance as a gemstone.