Name/Title
FluoriteEntry/Object ID
78.63.88Description
Chemical Composition: CaF2
Crystal System: Tetragonal System
Description: Common Name: Fluorite
Group Name:
Chemistry: CaF2
Location: Evanston, Illinois
Description: Dark purple crystal cluster (large-sized, 'chunky' crystals). Delmar: "Very translucent with well-formed cubes 1 -3/4 to 2 inches on a side, interpenetrating one another, with small cubic 'outlines' on the crystal faces."
PHYSICAL CHARACTERISTICS:
Color is extremely variable and many times can be an intense purple, blue, green or yellow; also colorless, reddish orange, pink, white and brown. A single crystal can be multi-colored.
Luster is vitreous.
Transparency: Crystals are transparent to translucent.
Crystal System: Isometric; 4/m bar 3 2/m
Crystal Habits include the typical cube and to a lesser extent, the octahedron as well as combinations of these two and other rarer isometric habits. Always with equant crystals; less common are crusts and botryoidal forms. Twinning also produces penetration twins that look like two cubes grown together.
Cleavage is perfect in 4 directions forming octahedrons.
Fracture is irregular and brittle.
Hardness is 4
Specific Gravity is 3.1+ (average)
Streak is white.
Other Characteristics: Often fluorescent blue or more rarely green, white, red or violet and may be thermoluminescent, phosphorescent and triboluminescent.
Associated Minerals are many and include calcite, quartz, willemite, barite, witherite, apatite, chalcopyrite, galena, sphalerite, pyrite and other sulfides.
Best Field Indicators are crystal habit, color zoning, hardness (harder than calcite, but softer than quartz or apatite), fluorescence and especially the octahedral cleavage.
Fracture: subconchoidal
Hardness: 5 Apatite
Luster: Metallic
Occurrence: Notable Occurrences include in addition to those mentioned above Cumberland, England; Spain; China; Brazil; Morocco; Bancroft, Ontario, Canada; Naica, Chihuahua, Mexico; Germany; Elmwood, Tennessee; Rosiclare, Illinois; Fort Wayne, Indiana; Pugh Quarry and Wood County, Ohio; Nancy Hanks Mine, Colorado and many other USA localities as well as many other localities from around the world.
Fluorite not only is attractive in its own right but is often associated with other attractive minerals. Fluorite crystals will frequently accompany specimens of silver gray galena, brassy yellow pyrite, chalcopyrite or marcasite, golden barite, black sparkling sphalerite, intricately crystallized calcite and crystal clear quartz, even amethyst
Rock Type: Sedimentary
Specific Gravity: 2.5-2.7
Streak: white
Variety: Fluorite is a mineral with a veritable bouquet of brilliant colors. Fluorite is well known and prized for its glassy luster and rich variety of colors. The range of common colors for fluorite starting from the hallmark color purple, then blue, green, yellow, colorless, brown, pink, black and reddish orange is amazing and is only rivaled in color range by quartz. Intermediate pastels between the previously mentioned colors are also possible. It is easy to see why fluorite earns the reputation as "The Most Colorful Mineral in the World".
Fluorite has other qualities besides its great color assortments that make it a popular mineral. It has several different crystal habits that always produce well formed, good, clean crystals. The cube is by far the most recognized habit of fluorite followed by the octahedron which is believed to form at higher temperatures than the cube. Although the cleavage of fluorite can produce an octahedral shape and these cleaved octahedrons are popular in rock shops the world over, the natural (e.g. uncleaved) octahedrons are harder to find.
A rarer habit variety is the twelve sided dodecahedron however it is never seen by itself and usually modifies the cubic crystals by replacing the edges of the cube with one flat face of a dodecahedron. The tetrahexahedron is a twenty four sided habit that is also seen modifying the cubic habit. But instead of one face replacing each cubic edge, two faces modify the cube's edges. Occasionally combinations of a cube, dodecahedron and tetrahexahedron are seen producing an overall cubic crystal with no less that three minor parallel faces replacing each cubic edge. A fifth form is the hexoctahedron which modifies the cube by placing six very minor faces at each corner of the cube. Twinning is also common in fluorite and symmetrical penetration twins, especially from Cumberland England are much sought after by collectors.Collection
Delmar Smith Mineral CollectionAcquisition
Accession
78.63Source or Donor
Delmar Smith Crystal CollectionAcquisition Method
DonationDimensions
Width
4-3/16 inDepth
3-11/16 inLength
6-13/16 inDimension Notes
Dimension taken at widest pointsLocation
Location
Display Case
DS-8Room
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Curtis GardnerDate
May 24, 2023Notes
Added current locationLocation
Container
RightDrawer
BottomShelf
Right, RightWall
NorthBuilding
Founders RoomCategory
PermanentMoved By
Ray BlohmDate
February 20, 2012Location
Container
RightCabinet
Case # 39Wall
WestRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
Permanent
