Name/Title
Calcite / PyriteEntry/Object ID
2016.1.2Description
Chemical Composition: CaCO3
Crystal System: Hexagonal System
Description: Common name: Calcite / Pyrite
Composition : CaCO3 /FeS2
Group: Carbonates / Sulfides
Location: unknown
Description: Multiple calcite crystals of varying sizes with spire pyrite intrusions. some light tan matrix showing on top. Calcite is pale yellow trancelucent.
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.
Notable Occurrences include Pugh Quarry, Ohio; Rosiclare, Illinois; Franklin, New Jersey; Elmwood, Tennessee; Brush Creek and other Missouri, Wisconsin, Kansas and Oklahoma localities, USA; Andreasburg, Harz Mountains and Saxony, Germany; Brazil; Guanajuato, Mexico; Cornwall, Durham and Lancashire, England; Bombay area of India; Eskifjord, Iceland; many African localities as well as others around the world with their own unique varieties.
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.
Notable Occurrences include Illinois and Missouri, USA; Peru; Germany; Russia; Spain; and South Africa among many others.
Best Field Indicators are crystal habit, hardness, streak, luster and brittleness.
Fracture: conchoidal
Hardness: 3 Calcite
Luster: Glassy
Rock Type: Sedimentary
Specific Gravity: 2.7
Streak: white
Variety: There are several varieties of calcite and it would be impossible to describe them all. However there are a few standouts. Possibly the most well known of calcite's varieties is its most common form, the classic scalenohedron or "Dogtooth Spar" as it is sometimes called. This variety appears as a double pyramid or dipyramid, but is actually a distinctly different form. The point of the scalenohedron is sharp and resembles the canine tooth of a dog, hence the name. Beautiful clear colorless or amber-orange examples of this variety are considered classics and outstanding examples come from Pugh Quarry, Ohio; Cornwall, England and Elmwood, Tennessee but the variety is found worldwideCollection
RAGM Mineral CollectionDimensions
Height
4-1/2 inWidth
5 inLength
6-1/2 inLocation
Location
Room
storage (donation room)Building
Storage (Donation Room)Category
Permanent