Lavendulan

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Lavendulan
Lavendulan-112544.jpg
General
CategoryArsenate Minerals
Formula
(repeating unit)		NaCaCu5(AsO4)4Cl.5H2O Usually with some K, Co and Ni [1]
IMA symbol Lvd [2]
Strunz classification 8.DG.05
Dana classification42.9.4.2
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group P21/n [3]
Identification
Formula mass 1,062.00 g/mol
ColorBlue or greenish blue
Crystal habit Thin botryoidal crusts of minute radiating fibers or thin rectangular, pseudo-orthorhombic plates [1] [3]
Twinning Common [3]
Cleavage Good on {010}, distinct on {100} and {001}
Fracture Uneven
Tenacity Brittle
Mohs scale hardness2+1⁄2 [3] [4] [5] 2+1⁄2 to 3 [1]
Luster Vitreous to waxy, satiny in aggregates
Streak Light blue
Diaphaneity Translucent
Specific gravity 3.54 [3] [4] [5] 3.84 [1]
Optical propertiesBiaxial (−), nearly uniaxial (−)
Refractive index Nx = 1.645 Ny = 1.715 Nz = 1.725 [1]

Nx = 1.660 Ny = 1.715 Nz = 1.734 [3]
Nx = 1.66 Ny = 1.715 Nz = 1.734 [4]

omega = 1.748 epsilon = 1.645

Contents

[5]
Pleochroism O = pale blue to pale greenish blue, E = blue to greenish blue
Solubility Easily soluble in hydrochloric acid [6]
Other characteristicsNot radioactive
References [1] [3] [4] [5]

Lavendulan is an uncommon copper arsenate mineral, known for its characteristic intense electric blue colour. It belongs to the lavendulan group, which has four members:

Lemanskiite and lavendulan are dimorphs; they have the same formula but different structures. Lemanskiite is tetragonal, but lavendulan is monoclinic. [7] Lavendulan has the same structure as sampleite, and the two minerals form a series. [8] It is the calcium analogue of zdenĕkite and the arsenate analogue of sampleite.

Lavendulan was originally named for the lavender color of the "type" specimen, which has since been determined to be a mixture with no relationship to modern lavendulan. The mineral which is now called lavendulan is not a lavender blue color, and has no relationship to the "type" material from Annaberg. [3] It often contains potassium, cobalt and nickel as impurities.

Unit cell

Although lavendulan is monoclinic, the angle β is very close to 90°, making the mineral pseudo-orthorhombic. Most references describe the lavendulan unit cell as an orthorhombic cell containing 8 formula units (Z = 8) but Mindat.org describes a monoclinic unit cell with the length of the c axis halved, and only 4 formula units per unit cell (Z = 4) and space group P21/n. [3] Unit cell parameters are reported as

Physical properties

Lavendulan is a blue or greenish blue translucent mineral, with a vitreous to waxy luster, satiny in aggregates, and a light blue streak. It occurs as thin botryoidal crusts of minute radiating fibers or as thin rectangular, pseudo-orthorhombic plates, with cleavage in three directions, nearly perfect perpendicular to the b crystal axis, [4] and distinct perpendicular to the a and c axes. Twinning is common. [3] The mineral is brittle, with an uneven fracture. It is quite soft, with hardness 2.5, between gypsum and calcite, and relatively dense; its specific gravity is 3.84, close to that of topaz, and much denser than quartz (specific gravity 2.5 to 2.7). It is easily soluble in hydrochloric acid. [6]

Optical properties

The refractive index varies with the direction of propagation of the light, and varies between 1.64 and 1.75. This is quite high, between topaz and ruby. Lavendulan is biaxial (−), and most sources quote values for three refractive indices, for light travelling parallel to the three crystal axes. One source, [5] however, gives lavendulan as nearly uniaxial (−), and quotes only two refractive indices, for the ordinary and extraordinary rays.

Lavendulan is pleochroic, with O = pale blue to pale greenish blue and E = blue to greenish blue. [3] [5]

Environment

Lavendulan is a rare secondary mineral in the oxidised zone of some copper-arsenic deposits. [3]

Type locality

A lavender blue mineral was discovered in 1837 by Johann F. A. Breithaupt in Annaberg in the Ore Mountains, which is a mountainous region spanning the Czech Republic and Germany. [9] The mineral was named "lavendulan" after the color, and Annaberg was the designated type locality. [6] In 1853, Vogel found a specimen of lavendulan from Jáchymov, also in the Ore Mountains, which was similar in appearance and characteristics to the material from Annaberg. [6] In 1877 Goldsmith examined some specimens of a turquoise blue arsenate of copper from the cobalt deposits of San Juan, Chile, and announced that they were also lavendulan. [6]

Nearly fifty years later, In 1924, William Foshag announced that the Chilean material was entirely distinct from that from Jáchymov, and he determined that it was a new mineral, and gave it the name freirinite, from the locality, the Blanca Mine, Freirina, Huasca Province, Atacama Region, Chile. [6]

In 1957, however, Claude Guillemin found that lavendulan and freirinite from the type localities gave identical x-ray powder patterns, and freirinite was discredited as a mineral species. [8] Yet another fifty years passed, and in 2007 Geister et al. re-examined Breithaupt's type specimen and found that it was a mixture unrelated to modern lavendulan. The second locality where lavendulan was found is in the Czech Republic, so the type locality of the species was changed to there, namely Jáchymov, Ore Mountains, Karlovy Vary Region. [3] The type material is held at the Mining Academy, Freiberg, Germany, reference 20944. [5]

Occurrences

At the type locality, lavendulan occurs associated with erythrite and a cobalt molybdate originally called pateraite, but now discredited. [6] At San Juan, Chile, it is associated with erythrite, cuprite, malachite and cobaltian wad. [5] At the Cap Garonne Mine, Pradet, Var, Provence-Alpes-Côte d'Azur, France, associated minerals are chalcophyllite, cyanotrichite, parnauite, mansfieldite, olivenite, tennantite, covellite, chalcanthite, antlerite, brochantite and geminite. [5] It also occurs at Tsumeb, Namibia, associated with cuprian adamite, conichalcite, o'danielite, tsumcorite, fahleite, quartz, calcite and gypsum. [5]

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<span class="mw-page-title-main">Carminite</span> Anhydrous arsenate mineral containing hydroxyl

Carminite (PbFe3+2(AsO4)2(OH)2) is an anhydrous arsenate mineral containing hydroxyl. It is a rare secondary mineral that is structurally related to palermoite (Li2SrAl4(PO4)4(OH)4). Sewardite (CaFe3+2(AsO4)2(OH)2) is an analogue of carminite, with calcium in sewardite in place of the lead in carminite. Mawbyite is a dimorph (same formula, different structure) of carminite; mawbyite is monoclinic and carminite is orthorhombic. It has a molar mass of 639.87 g. It was discovered in 1850 and named for the characteristic carmine colour.

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Metarauchite is a member of the autunite group, found at the Jáchymov ore district, Czech Republic and in Schneeberg, Germany. The autunite group is a group of structured uranyl phosphates and arsenates; the other members of the group are autunite, bassetite, heinrichite, kahlerite, nováčekite-I, nováčekite-II, rauchite, sabugalite, saléeite, torbernite, uranocircite, uranospinite, and zeunerite. The mineral is named after Czech mineral collector Luděk Rauch, who died in the Jáchymov mines during mineral prospecting.

<span class="mw-page-title-main">Lemanskiite</span>

Lemanskiite is a mineral that was first discovered in a mine at Abundancia mine, El Guanaco mining district, Chile, with the ideal formula of NaCaCu5(AsO4)4Cl·3H2O. Originally, this mineral was discovered as being dimorphus with lavendulan, but in 2018 it was revised to only have 3 water molecules. Lemanskiite typically occurs as rosette-shaped aggregates of thin lamellar or needle-shaped aggregates, such as lammerite. Lemanskiite is dark sky blue with a light blue streak, it is brittle with an excellent cleavage plane. It was found on a dumping site in the abandoned Abundancia mine, El Guanaco mining district, Region II, Antofagasta Province, Chile The new mineral has been named after Chester S. Lemanski, Jr. This mineral and name were then approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association.

References

  1. 1 2 3 4 5 6 7 8 Dana, James Dwight (1997). Dana's new mineralogy : the system of mineralogy of James Dwight Dana and Edward Salisbury Dana (8th, entirely rewritten and greatly enl. ed.). New York: Wiley. ISBN   978-0471193104.
  2. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Lavendulan, Mindat.org , retrieved 28 June 2022
  4. 1 2 3 4 5 6 7 Barthelmy, David (2014). "Lavendulan Mineral Data". Webmineral.com. Retrieved 27 June 2022.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Lavendulan" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 14 March 2022.
  6. 1 2 3 4 5 6 7 Foshag, W.F. (1924). "Freirinite: a new mineral species". American Mineralogist. 9 (2): 30.
  7. ↑ Ondrus, P.; Veselovsky, F.; Skala, R.; Sejkora, J.; Pazout, R.; Fryda, J.; Gabasova, A.; Vajdak, J. (1 April 2006). "LEMANSKIITE, NaCaCu5(AsO4)4Cl{middle dot}5H2O, A NEW MINERAL SPECIES FROM THE ABUNDANCIA MINE, CHILE". The Canadian Mineralogist. 44 (2): 523–531. doi:10.2113/gscanmin.44.2.523.
  8. 1 2 "New Mineral Names". American Mineralogist. 42: 123. 1957.
  9. ↑ Foshag, W.F. (1 February 1924). "Note on lavendulan from Joachimstal, Bohemia". American Mineralogist. 9 (2): 29–30. Retrieved 5 February 2022.
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