Canasite

Short description: Silicate mineral

Canasite

General
Category| Mineral
Formula
(repeating unit)| K3Na3Ca5Si12O30(OH)4
Strunz classification| 09.DG.80
Dana classification| 78.05.04.01
Crystal system| Monoclinic
Crystal class| Monoclinic-Prismatic
Unit cell| 1,596.05
Identification
Color| Brownish Yellow, Green Yellow, Light Green
Twinning| Polysynthetic
Cleavage| Perfect 1 direction, good 1 direction
Fracture| Splintery
Mohs scale hardness| 5 - 6
|re|er}}| Vitreous
Streak| White, Clear
Diaphaneity| Transparent, translucent
Specific gravity| 2.707
Density| 2.707
Optical properties| Biaxial (-)
Refractive index| nα = 1.534
nβ = 1.538
nγ = 1.543
Birefringence| 0.009
Pleochroism| None
2V angle| Measured 58°
Calculated 84°
Dispersion| Weak
r > v
Fusibility| Easily fusible to a transparent glass
Solubility| Readily decomposed by acids
Other characteristics|  Radioactive 1.12% (K)
Major varieties
Fluorcanasite| K3Na3Ca5Si12O30F4 · H2O
Frankamenite| K3Na3Ca5(Si12O30)[F,(OH)]4·(H2O)

Canasite is a mineral whose name is derived from its chemical composition of calcium (Ca), sodium (Na), and silicon (Si).[2] It was approved in 1959 by IMA.

## Properties

It is a relatively rare mineral. It occurs as aggregates in charoite, creating cabochons when contrasted against swirling purple charoite. It is extremely rare for canasite to be faceted. As crystals, it occurs in a size up to 10 cms, but in platy aggregates it can reach up to 20 cms in size. It is also granular.[3] Twinning is usual, and can occur as polysynthetic, which is when multiple twins align in a parallel.[4] It has a barely detectable 1.12% potassium radioactivity based on the GRapi unit (Gamma Ray American Petroleum Institute Units).[5] It consists of mostly oxygen (41.98%), silicon (26.8%) and calcium (15.93%), but otherwise contains sodium (7.31%), potassium (6.22%), which gives its radioactive properties, fluorine (1.51%) and hydrogen (0.24%).[4] There are two varieties of canasite: fluorcanasite and frankamenite. Purple canasite may be confused with stichtite, but recent research has found that the mineral advertized as canasite is a new specimen.[6]

## Occurrences and localities

Canasite can be found in three localities, all three in Russia. In Khibiny massif, it grows in a differentiated alkalic massif in pegmatites, and in the Murun massif, it grows in charoitic rocks. It also occurs in the Kola Peninsula. In Khibiny massif, it is associated with titanite, eudialyte, orthoclase, nepheline, pyroxene, lamprophyllite and fenaksite, while the specimens from Murun massif are usually associated with charoite, tinaksite and miserite.[2]

## References

1. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W.
2. ↑ 2.0 2.1 "Canasite". https://www.mindat.org/min-878.html.
3. ↑ "Canasite" (in en-US). 2017-03-06. https://nationalgemlab.in/canasite/.
4. ↑ 4.0 4.1 "ClassicGems.net :: Canasite Gems ::". http://www.classicgems.net/gem_canasite.htm.
5. ↑ "Canasite Mineral Data". http://webmineral.com/data/Canasite.shtml.
6. ↑ "Canasite Value, Price, and Jewelry Information" (in en). https://www.gemsociety.org/article/canasite-jewelry-gemstone-information/.

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