File:Rose quartz (Oxford Pegmatite Field; Hibbs Quarry, Hebron, Maine, USA) (42778093344).jpg

Rose quartz from Maine, USA. (Maine Mineral & Gem Museum collection, Bethel, Maine, USA)

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 5400 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The silicates are the most abundant and chemically complex group of minerals. All silicates have silica as the basis for their chemistry. "Silica" refers to SiO2 chemistry. The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4. Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens "belong" to each silicon. The resulting formula for silica is thus SiO2, not SiO4.

The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2). All other silicates have silica + impurities. Many silicates have a significant percentage of aluminum (the aluminosilicates).

Quartz (silicon dioxide/silica - SiO2) is the most common mineral in the Earth's crust. It is composed of the two most abundant elements in the crust - oxygen and silicon. It has a glassy, nonmetallic luster, is commonly clearish to whitish to grayish in color, has a white streak, is quite hard (H≡7), forms hexagonal crystals, has no cleavage, and has conchoidal fracture. Quartz can be any color: clear, white, gray, black, brown, pink, red, purple, blue, green, orange, etc.

The pink coloration of rose quartz has been attributed to the presence of Ti+4 impurity or the presence of dumortierite-like fibers. Some rose quartz coloration has been attributed to radiation bombardment of quartz having Al and P impurities.

The rose quartz shown above is from a pegmatitic granite body in the Oxford Pegmatite Field in Maine. Pegmatites are very coarsely-crystalline textured intrusive igneous rocks. Their large crystal size is the result of cooling of water-rich magmas. Pegmatites often have concentrations of unusual elements, which is conducive to the formation of less common minerals.

Locality: Hibbs Quarry, north of the town of Hebron, Oxford County, southwestern Maine, USA

Photo gallery of quartz and rose quartz: <a href="http://www.mindat.org/gallery.php?min=3337" rel="nofollow">www.mindat.org/gallery.php?min=3337</a> and