Name/Title
DolomiteEntry/Object ID
2009.62.81Description
Chemical Composition: CaMg(CO3)2
Crystal System: Triclinic System
Description: Common Name: Dolomite
Chemistry: CaMg(CO3)2, Calcium Magnesium Carbonate
Class: Carbonates
Location: Navarra, Spain
Description: Large twinned crystal clear with a smokey tint, rhomohedral in shape.
PHYSICAL CHARACTERISTICS:
Color is often pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron is present in the crystal.
Luster is pearly to vitreous to dull.
Transparency crystals are transparent to translucent.
Crystal System is trigonal; bar 3
Crystal Habits include saddle shaped rhombohedral twins and simple rhombs some with slightly curved faces, also prismatic, massive, granular and rock forming. Never found in scalenohedrons.
Cleavage is perfect in three directions forming rhombohedrons.
Fracture is conchoidal.
Hardness is 3.5-4
Specific Gravity is 2.86 (average)
Streak is white.
Other Characteristics: Unlike calcite, effervesces weakly with warm acid or when first powdered with cold HCl.
Associated Minerals: include calcite, sulfide ore minerals, fluorite, barite, quartz and occasionally with gold.
Best Field Indicators are typical pink color, crystal habit, hardness, slow reaction to acid, density and luster.
Fracture: conchoidal
Hardness: 3 Calcite
Luster: Vitreous
Occurrence: Dolomite in addition to the sedimentary beds is also found in metamorphic marbles, hydrothermal veins and replacement deposits.
Rock Type: Sedimentary
Specific Gravity: 2.86
Streak: white
Variety: Dolomite is a common sedimentary rock-forming mineral that can be found in massive beds several hundred feet thick all over the world and are quite common in sedimentary rock sequences. These rocks are called appropriately enough dolomite or dolomitic limestone. Dolomite at present time, does not form on the surface of the earth; yet massive layers of dolomite can be found in ancient rocks. That is quite a problem for sedimentologists who see sandstones, shales and limestones formed today almost before their eyes. Why no dolomite? Well there are no good simple answers, but it appears that dolomite rock is one of the few sedimentary rocks that undergoes a significant mineralogical change after it is deposited. They are originally deposited as calcite/aragonite rich limestones, but during a process call diagenesis the calcite and/or aragonite is altered to dolomite. The process is not metamorphism, but something just short of that. Magnesium rich ground waters that have a significant amount of salinity are probably crucial and warm, tropical near ocean environments are probably the best source of dolomite formation.Collection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationDimensions
Height
2-1/4 inWidth
3 inLength
4-3/4 inWeight
1.59 ozDimension Notes
Dimension taken at widest pointsLocation
Location
Display Case
FS-9Room
Frieda Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Ian CunninghamDate
December 27, 2023