Pectolite
Pectolite is a white to gray mineral, NaCa2Si3O8(OH), sodium calcium hydroxide inosilicate. It crystallizes in the triclinic system typically occurring in radiated or fibrous crystalline masses. It has a Mohs hardness of 4.5 to 5 and a specific gravity of 2.7 to 2.9. The gemstone variety, larimar, is a pale to sky blue.
Pectolite | |
---|---|
![]() | |
General | |
Category | Inosilicate mineral |
Formula (repeating unit) | NaCa2Si3O8(OH) |
Crystal system | Triclinic |
Crystal class | Pinacoidal (1) (same H-M symbol) |
Space group | P1 |
Unit cell | a = 7.99 Å, b = 7.03 Å, c = 7.03 Å; α = 90.51°, β = 95.21°, γ = 102.53°; Z = 2 |
Identification | |
Color | Colorless, whitish, grayish, yellowish |
Crystal habit | Tabular to acicular, radiating fibrous, spheroidal, or columnar; massive |
Twinning | Twin axis [010] with composition plane [100], common |
Cleavage | Perfect on {100} and {001} |
Fracture | Uneven |
Tenacity | Brittle; tough when compact |
Mohs scale hardness | 4.5 - 5 |
Luster | Silky, subvitreous |
Streak | White |
Diaphaneity | Translucent to opaque |
Specific gravity | 2.84 - 2.90 |
Optical properties | Biaxial (+) |
Refractive index | nα = 1.594 - 1.610 nβ = 1.603 - 1.614 nγ = 1.631 - 1.642 |
Birefringence | δ = 0.037 |
2V angle | Measured: 50° to 63°, Calculated: 42° to 60° |
Dispersion | r > v weak to very strong |
References | [1][2][3] |
Occurrence
It was first described in 1828 at Mt. Baldo, Trento Province, Italy and named from the Greek pektos – "compacted" and lithos – "stone".[2][3]
It occurs as a primary mineral in nepheline syenites, within hydrothermal cavities in basalts and diabase and in serpentinites in association with zeolites, datolite, prehnite, calcite and serpentine. It is found in a wide variety of worldwide locations.
gollark: <@199529131224989696> I was thinking about stuff recently, and you know when you said `allow for introspection, imagination and probably also analysis of the outside world` when I asked `What does consciousness actually do, though?`Maybe you would need some form of consciousness, whatever that is, for introspection, but you don't for "imagination" and "analysis of the outside world". You can do those with simple "AI" like we use for games.
gollark: !txet sdrawkcab em eviG
gollark: Unfortunately.
gollark: Yes, xkcd advertised it some years back.
gollark: U+202E is fun too but discord has no support.
See also
- Sérandite - the manganese analogue
References
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.