Calcite on Quartz

Object/Artifact

-

Crater Rock Museum

Name/Title

Calcite on Quartz

Entry/Object ID

2004.1.158

Description

Chemical Composition: Zn4 Si2 O7 (OH)2 -H2O Crystal System: Orthorhombic System Description: Common Name: Quartz Group Name: Chemistry: SiO2 , Silicon dioxide Location: Description: PHYSICAL CHARACTERISTICS: Color is as variable as the spectrum, but clear quartz is by far the most common color followed by white or cloudy (milky quartz). Purple (Amethyst), pink (Rose Quartz), gray or brown to black (Smoky Quartz) are also common. Cryptocrystalline varieties can be multicolored. Luster is glassy to vitreous as crystals, while cryptocrystalline forms are usually waxy to dull but can be vitreous. Transparency: Crystals are transparent to translucent, cryptocrystalline forms can be translucent or opaque. Crystal System is trigonal; 3 2. Crystal Habits are again widely variable but the most common habit is hexagonal prisms terminated with a six sided pyramid (actually two rhombohedrons). Three of the six sides of the pyramid may dominate causing the pyramid to be or look three sided. Left and right handed crystals are possible and identifiable only if minor trigonal pyramidal faces are present. Druse forms (crystal lined rock with just the pyramids showing) are also common. Massive forms can be just about any type but common forms include botryoidal, globular, stalactitic, crusts of agate such as lining the interior of a geode and many many more. Cleavage is very weak in three directions (rhombohedral). Fracture is conchoidal. Hardness is 7, less in cryptocrystalline forms. Specific Gravity is 2.65 or less if cryptocrystalline. (average) Streak is white. Associated Minerals are numerous and varied but here are some of the more classic associations of quartz (although any list of associated minerals of quartz is only a partial list): amazonite a variety of microcline, tourmalines especially elbaite, wolframite, pyrite, rutile, zeolites, fluorite, calcite, gold, muscovite, topaz, beryl, hematite and spodumene. Best Field Indicators are first the fact that it is very common (always assume transparent clear crystals may be quartz), crystal habit, hardness, striations, good conchoidal fracture and lack of good cleavage Common Name: Calcite Chemistry: CaCO3, Calcium Carbonate PHYSICAL CHARACTERISTICS: 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. 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: 5 Apatite Luster: Vitreous Occurrence: of amethyst are Brazil, Uraguay, Mexico, Russia, Thunder Bay area of Canada, and some locallities in the USA. For Smoky Quartz; Brazil, Colorado, Scotland, Swiss Alps among many others. Rose Quartz is also wide spread but large quantities come from brazil as do the only large find of Rose Quartz prisms. Natural citrine is found with many amethyst deposits but in very rare quantities. Fine examples of Rock crystal come from Brazil (again), Arkansas, many localities in Africa, etc. Fine Agates are found in, of course, Brazil, Lake Superior region, Montana, Mexico and Germany. 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. Specific Gravity: 3.4 Streak: White Variety: Amethyst is the purple gemstone variety. Citrine is a yellow to orange gemstone variety that is rare in nature but is often created by heating Amethyst. Milky Quartz is the cloudy white variety. Prasiolite is a leek-green gemstone variety that is rare in nature but is created by heating Amethyst from certain locations. Rock crystal is the clear variety that is also used as a gemstone. Rose quartz is a pink to reddish pink variety. Smoky quartz is the brown to gray variety. There are several varieties of calcite and it would be impossible to describe them all.

Collection

Suomynona Mineral Collection

Acquisition

Accession

2004.1

Source or Donor

Suomynona Mineral Collection

Acquisition Method

Donation

Dimensions

Dimension Notes

Dimension taken at widest points

Location

Location

Room

Neil Johnson

Building

Attic Storage

Category

Permanent