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Dolomite Pearl Spar

The Mineral dolomite




Dolomite is a very common mineral and is best known for its saddle-shaped curved crystal aggregates. 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. The occurence of Kolwezi, in the Congo (Zaire) has produced some fascinating, cobalt-rich specimens that are a beautiful hot pink color and are extremely popular.

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 scalenohedral crystakss, whereas minerals of the Calcite Group do.

Dolomite is both a mineral and a rock. The mineral is the pure form, and Dolomite rock is composed mostly of Dolomite but also with impurities such as Calcite, Quartz, and Feldspar.
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, yellow, and orange. Rarely yellow, green, red, and black.
Streak White
Hardness 3.5 - 4
Crystal System Hexagonal
3D Crystal Atlas
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Crystal Forms
and Aggregates
Dolomite most commonly forms in groups of small rhombohedral crystals very often with curved, saddle-like faces. Also occurs prismatic, (although usually slightly curved), grainy, botryoidal, coxcomb, and massive. A rare form from a few locations is as colorless transparent rhombohedrons or rhombohedral aggregates.
Transparency Transparent to translucent on thin splinters
Specific Gravity 2.8 - 3.0
Luster Vitreous, pearly
Cleavage 1,3 - rhombohedral
Fracture Conchoidal
Tenacity Brittle
Other ID Marks Occasionally fluoresces bluish-white or pink in shortwave ultraviolet light.
Complex Tests Effervesces in hydrochloric acid. Slowly dissolves in nitric acid and hydrochloric acids.
In Group Carbonates;
Striking Features Curved crystals and crystal groupings, associate minerals and environment
Environment In sedimentary rock, usually in dolomite rock or limestone. Also occasionally in high-temperature metamorphic rocks and low-temperature hydrothermal veins.
Rock Type Sedimentary, Metamorphic
Popularity (1-4) 2
Prevalence (1-3) 1
Demand (1-3) 1

Dolomite ON EBAY

VARIETIES
 -  Hot-pink, cobalt-rich variety of Dolomite.
 -  Rock composed mostly of the mineral Dolomite, but also contains impurities such as Calcite, Quartz, and Feldspar.
 -  Grouping of white to pinkish curved Dolomite crystals with a pearly luster.

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 and the hot-pink variety from the Congo are rare and unusual, and are sought after by collectors. Dolomite is useful in the chemical industry in the preparation of magnesium salts. It is also used in soil mixtures to lower the acid levels of the soil. Dolomite Rock is used as an ornamental and structural stone, and for extracting certain metals from their ores.

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. The most prominent European occurrence is Eugui, Navarra, Spain, where clear, transparent crystals, unlike any others were found. Other European localities are the Traversella, Piedmont, Italy; Binn Tal, Wallis, Switzerland; Styria, Austria; the Castilla quarry, Setiles, Spain; and Kapnik, Maramures Co., Romania.

 Two very important African deposits famous among collectors for the hot-pink cobalt-rich Dolomite are Kolwezi, Katanga (Shaba), Congo (Zaire), and Bou Azzer, Morocco. Another African occurrence of note is Tsumeb, Namibia. Other rich worldwide deposits are the Shangbao mine, Hunan Province, China; Brumado, Bahia, Brazil; and Santa Eulalia, Chihuahua, Mexico.

In Canada it has been found in Mont Saint-Hilaire, Quebec; and in the the area of Ontario, Canada adjacent to Lake Ontario, where this Dolomite body stretches accross the border to New York State where productive Dolomite occurrences exist along the Erie Canal and Mohawk River area. The best U.S. occurrences are in the tri-state mining district of Missouri, Kansas, and Oklahoma, especially the localities of Picher and Joplin, Ottawa Co., Oklahoma, where curved groups of lustrous pink, peach, and white crystals occured with Galena, Sphalerite, and Chalcopyrite. Two other famous Midwest localities are Black Rock, Lawrence Co., Arkansas; and the Sweetwater Mine, Reynolds Co., Missouri. Dolomite was also found in Pennsylvania in the Binkley-Ober Quarry, East Petersburg, Lancaster Co.

COMMON MINERAL ASSOCIATIONS
Calcite, Pyrite, Chalcopyrite, Sphalerite, Marcasite, Galena, Fluorite, Celestine, Gypsum, Barite, Siderite, Quartz

DISTINGUISHING SIMILAR MINERALS
Calcite - Softer (3), easily effervesces in cold, dilute hydrochloric acid, lacks rounded crystals.
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.


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