Ferberite / Fluorite / Quartz

Object/Artifact

-

Crater Rock Museum

Name/Title

Ferberite / Fluorite / Quartz

Entry/Object ID

2004.1.176

Description

Chemical Composition: SEE DESCRIPTION Crystal System: Orthorhombic System Description: Common Name: Ferberite / Fluorite / Quartz Chemistry: FeWO4, Iron Tungstate / CaF2, Calcium Fluoride / SiO2 , Silicon dioxide Group: Sulfates / Halides / Silcate Location: Description: Small, black ferberite crystals as a matrix, with intermixed areas of light blue to light green fluorite crystals on one side of the specimen, with small groupings of clear quartz crystals on the back. PHYSICAL CHARACTERISTICS OF FERBERITE: Color is Black. Luster is submetallic. Transparency crystals are opaque. Crystal System is monoclinic; 2/m Crystal Habits include the flat, heavily modified, tabular crystals. The crystals are elongated along the b axis and are generally flattened in the a axis direction. Also as columnar aggregates and lamellar masses. Cleavage is perfect in one direction parallel to the a and c axes. Fracture is uneven. Hardness is 4 - 4.5. Specific Gravity is approximately 7.6 (heavy even for metallic minerals) Streak is black. Associated Minerals are quartz, hematite, tourmalines, cassiterite, micas and pyrite. Other Characteristics: crystals are often striated. Best Field Indicators are crystal habit, color, density, luster and cleavage. THE PHYSICAL CHARACTERISTICS OF FLUORITE: 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. PHYSICAL CHARACTERISTICS OF QUARTZ: 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. Other Characteristics: Striations on prism faces run perpendicular to C axis, piezoelectric (see tourmaline) and index of refraction is 1.55. 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 Fracture: conchoidal Hardness: 3 Calcite Luster: Vitreous Occurrence: Ferberite typically occurs in pegmatites, granitic greisens and high temperature hydrothermal deposits. It is a minor ore of tungsten. Fluorite may occur as a vein deposit, especially with metallic minerals, where it often forms a part of the gangue (the surrounding "host-rock" in which valuable minerals occur) and may be associated with galena, sphalerite, barite, quartz, and calcite. It is a common mineral in deposits of hydrothermal origin and has been noted as a primary mineral in granites and other igneous rocks and as a common minor constituent of dolostone and limestone. Quartz occurs in hydrothermal veins as gangue along with ore minerals. Large crystals of quartz are found in pegmatites. Well-formed crystals may reach several meters in length and weigh hundreds of kilograms. Rock Type: Sedimentary Specific Gravity: 2.2 Streak: white Variety: Ferberite is the iron endmember of the manganese - iron wolframite solid solution series. Fluorite is a widely occurring mineral which is found in large deposits in many areas. Quartz is the second most abundant mineral in the Earth's continental crust, after feldspar.

Collection

Suomynona Mineral Collection

Acquisition

Accession

2004.1

Source or Donor

Suomynona Mineral Collection

Acquisition Method

Donation

Dimensions

Width

3 in

Depth

2-3/16 in

Length

4-1/2 in

Weight

21.58 oz

Dimension Notes

Dimension taken at widest points

Location

Location

Display Case

FS-11

Room

Frieda Smith Hall

Building

Crater Rock Museum

Category

Permanent