DOLOMITE
dolomite - mineral 14.2.1.1

	Chemical Formula	CaMg(CO3)2
	Composition	Calcium magnesium carbonate. The amount of calcium and magnesium in most specimens is equal, but occasionally one element may have a slightly greater presence than the other. Small amounts of iron and manganese are sometimes also present.
	Variable Formula	(Ca,Mg)2(CO3)2 (Ca,Mg,Fe,Mn)2(CO3)2
	Color	Colorless, white, gray, peach, pink. Sometimes yellow, green, and black.
	Streak	White
	Hardness	3½ - 4
	Crystal Forms and Aggregates	(Hexagonal) Dolomite most commonly forms in groups of small rhombohedral crystals with curved, saddle-like faces. It also occurs, although less commonly, as single rhombohedrons (which also have curved faces). Also occurs prismatic (usually slightly curved), grainy, and massive.
	Transparency	Transparent to translucent on thin splinters
	Specific Gravity	2.8 - 3.0
	Luster	Vitreous to pearly
	Cleavage	1,3 - rhombohedral
	Fracture	Conchoidal
	Tenacity	Brittle
	Other ID Marks	Occasionally fluoresces bluish-white or pink in shortwave ultraviolet light
	Varieties	Pearl Spar - Grouping of white to pinkish curved Dolomite crystals with a pearly luster. Dolomite Rock - Rock composed mostly of the mineral Dolomite, but also contains impurities such as Calcite, Quartz, and Feldspar.
	In Group	Carbonates ; Unclassified carbonates
	All About	Dolomite occurs in a different crystal class than the Calcite Group. This can be noted by the fact that Dolomite generally forms more elongated crystals than the Calcite Group. In addition, Dolomite never occurs in scalenohedrons, whereas minerals of the Calcite Group do. A unique, isolated Dolomite occurrence in Eugui, Spain has provided colorless transparent crystals that resemble the Iceland Spar variety of Calcite, and have no resemblance to Dolomite specimens from any other localities.
	Uses	Dolomite is used to make magnesia, which has important medicinal applications. Dolomite specimens from the Picher, Oklahoma area are very popular among mineral collectors and dealers. The clear transparent specimens from Spain are rare and unusual, and are in high demand by collectors. Dolomite Rock is used as an ornamental and structural stone, and for extracting certain metals from their ores. It is useful in the chemical industry in the preparation of magnesium salts.
	Striking Features	Curved crystals and crystal groupings, associate minerals
	Complex Tests	Powder effervesces in hydrochloric acid. Slowly dissolves in nitric and hydrochloric acids.
	Popularity (1-4)	2
	Prevalence (1-3)	1
	Demand (1-3)	1
	Distinguishing Similar Minerals	Calcite - softer (3), easily effervesces in cold, dilute hydrochloric acid Aragonite - lacks the cleavage of Dolomite, crystals not curved Quartz - much harder (7) Gypsum - much softer (2), is sectile and slightly flexible Anhydrite - different cleavage, does not effervesce Magnesite - massive and fine-grained specimens cannot be distinguished from Dolomite by ordinary methods.
	Commonly Occurs With	Calcite, Pyrite, Chalcopyrite, Sphalerite, Marcasite, Galena, Fluorite, Celestine, Gypsum, Barite, Siderite, Quartz
	Noteworthy Localities	There are many localities that produced fine Dolomite specimens. Most locations are in regions which contain an abundance of this mineral throughout the region. These regions are: Binnental, Switzerland; Piedmont, Italy; Cornwall, England; Freiberg and Scheenberg, Germany; Bahia, Brazil; Guanjuanato, Mexico; the tri-state mining district of Missouri, Kansas, and Oklahoma; the Mother Lode District of California; Colorado; North Carolina; the area of Ontario adjacent to the Great Lakes. Two exceptional occurrences are: 1) Eugui, Navarra, Spain, where clear, transparent crystals, unlike any others, were found, and 2) Picher, Ottawa Co., Oklahoma, where curved groups of lustrous pink, peach, and white crystals occur with Galena, Sphalerite, and Chalcopyrite in abundance. Dolomite was also found in Rochester, Monroe Co., New York and Franklin, Sussex Co., New Jersey.
	Picture Icon Links	1.   2.
	Picture Links	1. Curved pink crystals ("Pearl Spar") 2. White Dolomite with Chalcopyrite

Additional references:

• The Mineral Gallery (Amethyst Galleries)
• Mineralogy Database (David Barthelmy)
• Alkali-Nuts (Marc Favre)