Name/Title
Calcite var. Cobaltian CalciteEntry/Object ID
2004.1.116Description
Chemical Composition: CoCaCO3
Crystal System: Tetragonal System
Description: Common Name: Calcite var Cobaltian Calcite
Class Name: Carbonates
Group Name: Calcite
Chemistry: CoCaCO3 Cobalt Calcium Carbonate
Location: Katanga Copper Zone, Katanga, Congo, Africa
Description: Bright pink calcite crystals on a grey limestone matrix
PHYSICAL CHARACTERISTICS OF CALCITE:
Color is extremely variable but generally white or colorless or with light shades of yellow, orange, blue, pink, red, brown, green, black and gray. Occasionally iridescent.
Luster is vitreous to resinous to dull in massive forms.
Transparency: Crystals are transparent to translucent.
Crystal System is trigonal; bar 3 2/m
Crystal Habits are extremely variable with almost any trigonal form possible. Common among calcite crystals are the scalenohedron, rhombohedron, hexagonal prism, and pinacoid. Combinations of these and over three hundred other forms can make a multitude of crystal shapes, but always trigonal or pseudo-hexagonal. Twinning is often seen and results in crystals with blocky chevrons, right angled prisms, heart shapes or dipyramidal shapes. A notch in the middle of a doubly terminated scalenohedron is a sure sign of a twinned crystal. lamellar twinning also seen resulting in striated cleavage surfaces. Pseudomorphs after many minerals are known, but easily identified as calcite. Also massive, fibrous, concretionary, stalactitic, nodular, oolitic, stellate, dendritic, granular, layered, etc. etc.
Cleavage is perfect in three directions, forming rhombohedrons.
Fracture is conchoidal.
Hardness is 3 (only on the basal pinacoidal faces, calcite has a hardness of less than 2.5 and can be scratched by a fingernail).
Specific Gravity is approximately 2.7 (average)
Streak is white.
Other Characteristics: refractive indices of 1.49 and 1.66 causing a significant double refraction effect (when a clear crystal is placed on a single line, two lines can then be observed), effervesces easily with dilute acids and may be fluorescent, phosphorescent, thermoluminescence and triboluminescent.
Associated Minerals are numerous but include these classic associations: Fluorite, quartz, barite, sphalerite, galena, celestite, sulfur, gold, copper, emerald, apatite, biotite, zeolites, several metal sulfides, other carbonates and borates and many other minerals.
Best Field Indicators are crystal habit, reaction to acid, abundance, hardness, double refraction and especially cleavage.
Fracture: conchoidal
Hardness: 3 Calcite
Luster: Vitreous
Occurrence: Calcite, which gets its name from "chalix" the Greek word for lime, is a most amazing and yet, most common mineral. It is one of the most common minerals on the face of the Earth, comprising about 4% by weight of the Earth's crust and is formed in many different geological environments. Calcite can form rocks of considerable mass and constitutes a significant part of all three major rock classification types. It forms oolitic, fossiliferous and massive limestones in sedimentary environments and even serves as the cements for many sandstones and shales. Limestone becomes marble from the heat and pressure of metamorphic events. Calcite is even a major component in the igneous rock called carbonatite and forms the major portion of many hydrothermal veins. Some of these rock types are composed of better than 99% calcite.
Calcite is intricately tied to carbon dioxide in another way. Since many sea organisms such as corals, algae and diatoms make their shells out of calcite, they pull carbon dioxide from the sea water to accomplish this in a near reverse of the reaction above. This is fortuitous for us, as carbon dioxide has been found to be a green house gas and contributes to the so called "green house gas effect". Environmentally then, calcite is very important and may have been quite important to the successful development of our planet in the past. By pulling carbon dioxide out of the sea water, this biological activity allows more of the carbon dioxide in the air to dissolve in the sea water and thus acts as a carbon dioxide filter for he planet. Environmentalists are now actively engaged in determining if this activity can be increase by human intervention to the point of warding off the "green house gas effect". A significant amount of calcite precipitation in sea water is undoubtedly inorganic, but the exact amount that this contributes is not well known. Calcite and other carbonate minerals are very important minerals in the ocean ecosystems of the world.
Rock Type: Sedimentary
Specific Gravity: 2.7
Streak: white
Texture: crystaline
Variety: With calcite so abundant and so widely distributed it is no wonder that it can be so varied. The crystals of calcite can form literally a thousand different shapes by combining the basic forms of the positive rhombohedron, negative rhombohedron, steeply, moderately and slightly inclined rhombohedrons, various scalahedrons, prism and pinacoid to name a few of the more common forms. There are more than 300 crystal forms identified in calcite and these forms can combine to produce the thousand different crystal variations. Calcite also produces many twin varieties that are favorites among twin collectors. There are also phantoms, included crystals, color varieties, pseudomorphs and unique associations. There simply is no end to the varieties of calcite.Collection
Suomynona Mineral CollectionAcquisition
Accession
2004.1Source or Donor
Suomynona Mineral CollectionAcquisition Method
DonationOther Name
Calcite var CobaltianDimensions
Width
7 inDepth
4 inLength
8 inWeight
11.35 ozDimension Notes
Dimension taken at widest pointsLocation
Category
PermanentMoved By
Curtis GardnerDate
May 24, 2023Notes
Added current locationLocation
Drawer
3rd from leftShelf
Bottom East, Bottom EastWall
North 2nd centerHallway
Discovery HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Scott LonganDate
August 21, 2009
