| Canasite | |
|---|---|
 | |
| General | |
| Category | Minerals |
| Formula | K3Na3Ca5Si12O30(OH)4 |
| IMA symbol | Cns[1] |
| 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 |
| Luster | 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 byIMA.
It is a relatively rare mineral. It occurs as aggregates incharoite, 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 aspolysynthetic, 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 itsradioactive properties, fluorine (1.51%) and hydrogen (0.24%).[4] There are two varieties of canasite:fluorcanasite andfrankamenite. Purple canasite may be confused withstichtite, but recent research has found that the mineral advertized as canasite is a new specimen.[6]
Canasite has been found in three localities, all 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 withtitanite,eudialyte,orthoclase,nepheline,pyroxene,lamprophyllite andfenaksite, while the specimens from Murun massif are usually associated withcharoite,tinaksite andmiserite.[2]