A glassy, variously colored calcium phosphates used as a source of phosphorous to be used in fertilizer, rarely as a gemstone, and as a mineral specimen.

The name from chalix, the Greek word for lime.

It is a most common mineral and one of the most common minerals on the face of the earth, consisting of about four percent by weight of the earth's crust and is formed in many different geological environments.

It is used in cements and mortars, in the production of lime, and limestone is used in the steel industry; in the glass industry, as ornamental stone, in chemical and optical uses, and as mineral specimens.

1. Native aluminum oxide, the hardest naturally occurring mineral known apart from diamond (corundum rates 9 on the Mohs scale of hardness).

A lack of cleavage also increases its durability. Its crystals are barrel-shaped prisms of the trigonal system.

2. The second hardest natural mineral known to science.

Its two varieties are sure to be on any list of gemstones. The red variety of corundum is known as ruby and all the other colors of corundum are known as sapphire.

Besides being used as gemstones, it is also utilized as an abrasive.

The ultimate gemstone, having few weaknesses and many strengths.

It is well known that diamond is the hardest substance found in nature, but few people realize that diamond is four times harder than the next hardest natural mineral, corundum (sapphire and ruby).

Diamond is usually utilized as a gemstone and an abrasive, as well as in scientific uses.

A well known mineral prized for its glassy luster and rich variety of colors.

Used as a flux in iron smelting, a rare gemstone, a source of fluorine, as special optical lenses, and a popular mineral specimen.

1. One of the more common minerals in sedimentary environments used in plaster, wall board, some cements, fertilizer, paint filler, ornamental stone, etc.
2. A common white or colorless mineral (hydrated calcium sulphate) used to make cements and plasters; especially, plaster of Paris.

A polymorph of other minerals that share the same chemistry, but have different crystal structures.

Used as mineral specimens and in the porcelain industry.

Used as an ornamental and heat, acid and electrically-resistant stone (soapstone) used as counter tops, electrical switchboards, carvings, etc.; as an ingredient in paints, rubber, roofing materials, ceramics, and insecticides. Most commonly known as the primary ingredient in talcum powder.

A common gemstone that has been used for centuries in jewelry and its optical properties are useful in industry.