Rubicline

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Rubicline
Rubicline.jpg
General
Category Tectosilicate minerals, feldspar group
Formula (Rb, K)[AlSi3O8]
IMA symbol Rub [1]
Strunz classification 9.FA.30
Crystal system Triclinic
Crystal class Pinacoidal (1)
(same H-M symbol)
Space group P1
Identification
Formula mass 313.11 g/mol
ColorColorless
Cleavage {001}
Luster Vitreous
Diaphaneity Transparent
Density 2.8 g/cm3
Optical propertiesbiaxial
Refractive index nα = 1.520 nβ = 1.524 nγ = 1.527
Birefringence δ = 0.007
Dispersion Strong
Other characteristicsRadioactive
References [2] [3]

Rubicline, also referred to as Rb-microcline, is the rubidium analogue of microcline, an important tectosilicate mineral. Its chemical formula is (Rb, K)[AlSi3O8] with an ideal composition of RbAlSi3O8. Chemical analysis by electron microprobe indicated the average weight of the crystal is 56.66% SiO2, 16.95% Al2O3, and 23.77% Rb2O, [4] along with trace amounts of caesium oxide (Cs2O) and iron(III) oxide (Fe2O3). [5]

Rubicline was first discovered in 1998 in Elba, Italy, by a team from the University of Manitoba. It was the first mineral to have been discovered with rubidium as an essential constituent. [5] It has also been found in Mozambique [6] and the Kola Peninsula in Russia. [7] Rubicline occurs as small, abundant, rounded grains found within veins of rubidian microcline. Pure rubicline with an ideal potassium-free composition has never been found in nature. [4] Rubicline was synthesized in 2001 by placing powdered albite in a solvent of RbCl. This mixture was then placed in a silver tube containing H2O, heated to 400 °C and pressurized to 60  MPa. [4]

Unlike microcline, which can be yellow, red, or green, rubicline is colorless. It is also transparent, brittle, [5] and has a vitreous luster. [8] Rubicline has been classified as both triclinic and monoclinic. [4] [8] The crystal does not show twinning. Other minerals in this group include adularia, anorthoclase, buddingtonite, celsian, hyalophane, microcline, monalbite, orthoclase, and sanidine. [8]

Like all rubidium compounds, rubicline is mildly radioactive. Activity and dose rate of various amounts of rubicline are listed in the table below. [2]

Specimen weight/sizeCalculated
activity (Bq)		Calculated
activity (Ci)		Estimated
activity GR(api)		Estimated
exposure (mRem)/hr*
1000 g / 8.79 cm183,3554.96×10−68,449.312.78
100 g / 4.08 cm18,3364.96×10−7844.930.28
10 g / 1.89 cm1,8344.96×10−884.490.03
1 g / 8.79 mm1834.96×10−98.450.00
0.1 g / 4.08 mm184.96×10−100.840.00
0.01 g / 1.89 mm24.96×10−110.080.00
0.001 g / 0.88 mm04.96×10−120.010.00

References

  1. ↑ 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.
  2. 1 2 Rubicline at Webminerals
  3. ↑ Rubicline at Mindat
  4. 1 2 3 4 Kyono, A. & Kimata, M. (August 2001). "Refinement of the crystal structure of a synthetic non-stoichiometric Rb-feldspar" (PDF). Mineralogical Magazine. 65 (4): 523–531. Bibcode:2001MinM...65..523K. CiteSeerX   10.1.1.580.3483 . doi:10.1180/002646101750377542. S2CID   95219083.
  5. 1 2 3 Teertstra, David K.; et al. (December 2008). "Rubicline, a new feldspar from San Piero in Campo, Elba, Italy" . American Mineralogist. 83 (11–12): 1335–1339. doi:10.2138/am-1998-11-1223.
  6. ↑ Teertstra, D. K.; Cerny, P.; Hawthorne, F. C. (1999). "Subsolidus rubidium-dominant feldspar from the Morrua pegmatite, Mozambique: paragenesis and composition". Mineralogical Magazine. 63 (3): 313–320. Bibcode:1999MinM...63..313T. CiteSeerX   10.1.1.607.9008 . doi:10.1180/002646199548538. ISSN   0026-461X. S2CID   53607085.
  7. ↑ "Rubicline R070044". RRUFF. Retrieved 15 February 2010.
  8. 1 2 3 Ralph, Jolyon & Chau, Ida (2010). "Rubicline". Mindat.org. Retrieved 15 February 2010.
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