Fluorite, Schorl and Muscovite

ID	535
Mineral	Fluorite Schorl Muscovite
Location	Erongo Mountains - Karibib - Erongo - Namibia
Fluorescence	LW-UV: check SW-UV: check
Mindat.org	View Fluorite information at mindat.org View Schorl information at mindat.org View Muscovite information at mindat.org

Mindat data

ID	1576
Long ID	1:1:1576:5
Formula	`CaF₂`
IMA Status	0 1
Other Occurrences	Hydrothermal veins; cavities in sedimentary rocks; as a cementing material in sandstones; as hot springs deposits.
Industrial	Flux in steel making; source of fluorine
Discovery Year	1529
Diapheny	Transparent
Cleavage	Perfect on {111}, very easy.
Tenacity	brittle
Colour	Purple, lilac, golden-yellow, green, colourless, blue, pink, champagne, brown. See also https://www.mindat.org/mesg-631877.html
Hardness (min)	4.0
Hardness (max)	4.0
Luminescence	Fluorescent, Short UV=blue, Long UV=blue.
Lustre	Vitreous
About the name	Named in 1797 by Carlo Antonio Galeani Napione from the Latin, fluere = "to flow" (for its use as a flux). The term fluorescence is derived from fluorite, which will often markedly exhibit this effect. The element fluorine also derives its name from fluorite, a major source of the element.
Streak	White
Crystal System	Isometric
Cleavage Type	Perfect
Fracture type	Splintery,Sub-Conchoidal
Morphology	Fluorite has seven main crystal forms: the most common Are the cube {100}, octahedron {111} and dodecahedron {110}; these forms having fixed Miller indices); and the tetrahexahedron {hk0}, trapezohedron {h11}, trisoctahedron {hhl} and hexoctahedron {hkl} (less common to quite rare crystal forms, having variable Miller indices). Combinations of two or more of these forms are common. The cuboctahedron (combined cube and octahedron) is less common than the combination of a cube and a docecahedron, the cubododecahedron. The faces of some crystal forms are more easily etched by nature than other faces, although this also depends on other parameters, and so none of the forms will always be smooth. Not all crystal faces will always be present, and sometimes certain faces are more developed than others, even within the same crystal form. Consequently, elongated crystals of fluorite have been observed." Crystals distorted at times by unequal development of faces, as of {013}. Often markedly composite; minute cubes aggregated to form an octahedron at times or as an overgrowth of crystals upon the corners of an earlier formed crystal of differing habit. Massive; compact; earthy, columnar (rare), or in globular aggregates; botryoidal (rare). For the Goldschmidt images we currently show the following habits with the crystallographic forms denoted here: no. 1 : a cube {100} no. 2 : an octahedron {111} no. 3 : a dodecahedron {110} no. 12: a cube {100}, modified by a hexoctahedron {421} no. 45: a cube {100}, highly modified by a dodecahedron {110}, two tetrahexahedrons: {210} and {310}, and a trapezohedron {211} no. 66: an octahedron {111}, modified by a dodecahedron {110} and a trisoctahedron {221}
Twinning	On {111}, usually as interpenetrating cubes (e.g., Strzegom, Poland), but also as contact spinel twins (e.g. Naica, Mexico and Chumar Bakhoor, Pakistan).
UV	Blue under LW-UV, due to Eu²⁺; other colors caused by different activators (white & cream - organic matter). Red (Mapimi, Mexico), pink (Doña Ana claims, AZ), white (Sterling Hill, NJ). Green response points to ytterbium (Siddike et al. 2003). May also be phosphorescent.
Thermal Behaviour	Melting point 1360°C.
Comment Luster	Dull when massive
shortcode_ima	Flr
Group	Fluorite Group

ID	3578
Long ID	1:1:3578:7
Formula	`NaFe²⁺₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH)`
IMA Status	0 1
Occurrence	In placers.
Other Occurrences	In granites and granitic pegmatites, high temperature hydrothermal veins, metamorphic rocks.
Discovery Year	1505
Diapheny	Translucent,Opaque
Cleavage	Very poor on {11_20}, {10_11}
Tenacity	brittle
Colour	Bluish-black to black, sometimes brownish-black, rarely greenish-black.
Hardness (min)	7.0
Hardness (max)	7.0
Luminescence	Nonfluorescent.
Lustre	Vitreous to oily, dull.
About the name	The early history of the mineral schorl shows that the name "Schorl" was in use prior to the year 1400 (AD) because a village known today as Zschorlau (in Saxony, Germany) was then named "Schorl" (or minor variants of this name). This village had a nearby tin mine where, in addition to cassiterite, a lot of black tourmaline was found. First mentioned by Ulrich Rülein von Calw 1505. The first relatively detailed description of schorl with the name "schürl" and its occurrence (various tin mines in the Saxony Ore Mountains) was written by Johannes Mathesius (1504-1565) in 1562 under the title "Sarepta oder Bergpostill". Up to about 1600, additional names used in the German language were "Schurel", "Schörle", and "Schurl". From the 18th century on, the name "Schörl" was mainly used in the German-speaking area. In English, the names "shorl" and "shirl" were used in the 18th century for schorl. In the 19th century the names "common schorl", "schörl", "schorl" and "iron tourmaline" were used in the Anglo-Saxon area (Ertl, 2006).
Streak	Greyish-white to bluish-white.
Crystal System	Trigonal
Cleavage Type	Poor/Indistinct
Fracture type	Irregular/Uneven,Sub-Conchoidal
Morphology	Prismatic to acicular.
Twinning	Rarely on {10_10} and {40_41}.
Publication Year	1524
key_elements	0
shortcode_ima	Srl
Group	Tourmaline

ID	2815
Long ID	1:1:2815:4
Formula	`KAl₂(Si₃Al)O₁₀(OH)₂`
IMA Status	0 1
Other Occurrences	Muscovite is common in many different rock types as a primary mineral.
Diapheny	Transparent,Translucent
Cleavage	Perfect on {001}.
Tenacity	elastic
Colour	White to colorless, silvery-white, and tinged various colors by impurities.
Hardness (min)	2.5
Hardness (max)	2.5
About the name	The earliest names attributable to muscovite include Muscovy Glass, Cat Silver, and Lapis Specularis (stone mirror); these names appearing in texts in the seventeenth century and before. The stand-alone name 'Muscovite' was used as early as 1794 by Johann Gottfried Schmeisser in his System of Mineralogy and is derived from the term "Muscovy glass," which was in common use by that time. Muscovy Province in Russia yielded sheet mica for a variety of uses. Muscovite and sometimes similar species were earlier called mica (Phillips and Kersey, 1706), glimmer (Phillips and Kersey, 1706), and isinglass (1747 according to OED) but all of these terms are still in use to some degree. It should be noted that mica, glimmer, and isinglass were also used for a variety of materials before these given dates and in those earlier times did not always indicate what would be a mineral, much less muscovite proper. Isinglass, for example, was originally used for a gelatinous bladder found in sturgeon.
Streak	White
Crystal System	Monoclinic
Cleavage Type	Perfect
Fracture type	Micaceous
Morphology	Crystals uncommon, tabular {001} with rhombic to hexagonal outlines, often bound by {221}, {_111} and {010} (hkl refer to -2M^1 polytype). Less common as prismatic, parallel to [001], with a crude hexagonal cross section. Most typically found as "books" and as flaky grains in various rocks. Sometimes in plumose or fibrous aggregates.
Twinning	Mica law twins common [310] forming six pointed stars, less common with the composition plane perpendicular to {001} (hkl refer to -2M^1 polytype).
shortcode_ima	Ms
Group	Dioctahedral mica

Price: € 35

Dimensions: Not registered

Weight: Not registered

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Notes:

Symbol	Element
Al	Aluminium
B	Boron
Ca	Calcium
F	Fluorine
Fe	Iron
H	Hydrogen
K	Potassium
Na	Sodium
O	Oxygen
Si	Silicium

Fluorite, Schorl and Muscovite

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