Name/Title
Pyrite in CalciteEntry/Object ID
2009.62.98Description
Chemical Composition: see description
Crystal System: Tetragonal System
Description: Common Name: Calcite / Pyrite
Chemistry: CaCO3, Calcium Carbonate / FeS2, Iron Sulfide
Group: Carbonates / Sulfides
Location: Dong Shan, Hunan Province, China
Desciption: Large specimen with creamy pink crystals uniformly distributed on a light tan rocky base with one large and a few smaller pyrite crystals on one end .
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.
PHYSICAL CHARACTERISTICS OF PYRITE
Color is brassy yellow.
Luster is metallic.
Transparency: Crystals are opaque.
Crystal System is isometric; bar 3 2/m
Crystal Habits include the cube, octahedron and pyritohedron (a dodecahedron with pentagonal faces) and crystals with combinations of these forms. Good interpenetration twins called iron crosses are rare. Pyrite is commonly found in nodules. A flattened nodular variety called "Pyrite Suns" or "Pyrite Dollars" is popular in rock shops. Also massive or reniform and replaces other minerals and fossils forming pseudomorphs or copies.
Cleavage is very indistinct.
Fracture is conchoidal.
Hardness is 6 - 6.5
Specific Gravity is approximately 5.1+ (heavier than average for metallic minerals)
Streak is greenish black.
Other Characteristics: Brittle, striations on cubic faces caused by crossing of pyritohedron with cube. (note - striations on cube faces also demonstrate pyrite's lower symmetry). Pyrite (unlike gold) is not malleable.
Associated Minerals are quartz, calcite, gold, sphalerite, galena, fluorite and many other minerals. Pyrite is so common it may be quicker to name the unassociated minerals.
Best Field Indicators are crystal habit, hardness, streak, luster and brittleness.
Fracture: conchoidal
Hardness: 3 Calcite
Luster: Vitreous
Occurrence: Calcite is a common constituent of sedimentary rocks, limestone in particular, much of which is formed from the shells of dead marine organisms. Approximately 10% of sedimentary rock is limestone.
Calcite is the primary mineral in metamorphic marble. It also occurs as a vein mineral in deposits from hot springs, and it occurs in caverns as stalactites and stalagmites.
Calcite may also be found in volcanic or mantle-derived rocks such as carbonatites, kimberlites, or rarely in peridotites.
Pyrite is so common in the earth's crust that it is found in almost every possible environment, hence it has a vast number of forms and varieties.
Rock Type: Sedimentary
Specific Gravity: 2.7
Streak: white
Variety: 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.
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.
Pyrite is the classic "Fool's Gold". There are other shiny brassy yellow minerals, but pyrite is by far the most common and the most often mistaken for gold. Whether it is the golden look or something else, pyrite is a favorite among rock collectors. It can have a beautiful luster and interesting crystals.Collection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationDimensions
Width
8 inDepth
2-1/2 inLength
14-1/2 inWeight
11.3 ozDimension Notes
Dimension taken at widest pointsLocation
Category
PermanentMoved By
Curtis GardnerDate
May 24, 2023Notes
Added current location