Rubicline

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title: "Rubicline" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["rubidium-compounds", "triclinic-minerals", "minerals-in-space-group-2", "alkali-feldspar-series"] description: "Rubidium feldspar mineral" topic_path: "general/rubidium-compounds" source: "https://en.wikipedia.org/wiki/Rubicline" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Rubidium feldspar mineral ::

::data[format=table title="Infobox mineral"]

Field	Value
name	Rubicline
category	Tectosilicate minerals
group	Feldspar group
series	Alkali feldspar series
image	Rubicline.jpg
formula	(Rb, K)[AlSi3O8]
IMAsymbol	Rub
molweight	313.11 g/mol
strunz	9.FA.30
system	Triclinic
class	Pinacoidal ()
(same H-M symbol)
symmetry	P
color	Colorless
cleavage	{001}
luster	Vitreous
diaphaneity	Transparent
density	2.8 g/cm3
opticalprop	biaxial
refractive	nα = 1.520 nβ = 1.524 nγ = 1.527
birefringence	δ = 0.007
dispersion	Strong
other	Radioactive
references
::

| name = Rubicline | category = Tectosilicate minerals | group = Feldspar group | series = Alkali feldspar series | boxwidth = | boxbgcolor = | image = Rubicline.jpg | imagesize = | alt = | caption = | formula = (Rb, K)[AlSi3O8] | IMAsymbol = Rub | molweight = 313.11 g/mol | strunz = 9.FA.30 | dana = | system = Triclinic | class = Pinacoidal () (same H-M symbol) | symmetry = P | color = Colorless | habit = | twinning = | cleavage = {001} | fracture = | tenacity = | mohs = | luster = Vitreous | streak = | diaphaneity = Transparent | gravity = | density = 2.8 g/cm3 | polish = | opticalprop = biaxial | refractive = nα = 1.520 nβ = 1.524 nγ = 1.527 | birefringence = δ = 0.007 | pleochroism = | 2V = | dispersion = Strong | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = Radioactive | alteration = | references =

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, along with trace amounts of caesium oxide (Cs2O) and iron(III) oxide (Fe2O3).

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. It has also been found in Mozambique and the Kola Peninsula in Russia. 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. 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.

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

Like all rubidium compounds, rubicline is mildly radioactive. Activity and dose rate of various amounts of rubicline are listed in the table below. ::data[format=table] | Specimen weight/size | Calculated activity (Bq) | Calculated activity (Ci) | Estimated activity GR(api) | Estimated exposure (mRem)/hr* | |---|---|---|---|---| | 1000 g / 8.79 cm | 183,355 | 4.96×10−6 | 8,449.31 | 2.78 | | 100 g / 4.08 cm | 18,336 | 4.96×10−7 | 844.93 | 0.28 | | 10 g / 1.89 cm | 1,834 | 4.96×10−8 | 84.49 | 0.03 | | 1 g / 8.79 mm | 183 | 4.96×10−9 | 8.45 | 0.00 | | 0.1 g / 4.08 mm | 18 | 4.96×10−10 | 0.84 | 0.00 | | 0.01 g / 1.89 mm | 2 | 4.96×10−11 | 0.08 | 0.00 | | 0.001 g / 0.88 mm | 0 | 4.96×10−12 | 0.01 | 0.00 | ::

• If held in hand for one hour.
• Government estimate of average annual exposure (360 mRem)
• Max permissible adult dose 50,000 mRem/yr (hands), 15,000 mRem/yr (eyes)
• Lethal exposure 400,000 to 500,000 mRem

References

References

1. Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
2. [http://www.webmineral.com/data/Rubicline.shtml Rubicline at Webminerals]
3. [http://www.mindat.org/min-7276.html Rubicline at Mindat]
4. Teertstra, David K.. (December 2008). "Rubicline, a new feldspar from San Piero in Campo, Elba, Italy". American Mineralogist.
5. (1999). "Subsolidus rubidium-dominant feldspar from the Morrua pegmatite, Mozambique: paragenesis and composition". Mineralogical Magazine.
6. "Rubicline R070044". RRUFF.
7. (August 2001). "Refinement of the crystal structure of a synthetic non-stoichiometric Rb-feldspar". Mineralogical Magazine.
8. (2010). "Rubicline". Mindat.org.

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