Chemistry:Pectolite

From HandWiki
Short description: Silicate mineral
Pectolite
Pectolite-263712.jpg
General
CategoryInosilicate mineral
Formula
(repeating unit)
NaCa2Si3O8(OH)
Crystal systemTriclinic
Crystal classPinacoidal (1)
(same H-M symbol)
Space groupP1
Unit cella = 7.99 Å, b = 7.03 Å,
c = 7.03 Å; α = 90.51°,
β = 95.21°, γ = 102.53°; Z = 2
Identification
ColorColorless, whitish, grayish, yellowish
Crystal habitTabular to acicular, radiating fibrous, spheroidal, or columnar; massive
TwinningTwin axis [010] with composition plane [100], common
CleavagePerfect on {100} and {001}
FractureUneven
TenacityBrittle; tough when compact
Mohs scale hardness4.5 – 5
|re|er}}Silky, subvitreous
StreakWhite
DiaphaneityTranslucent to opaque
Specific gravity2.84 – 2.90
Optical propertiesBiaxial (+)
Refractive indexnα = 1.594 – 1.610 nβ = 1.603 – 1.614 nγ = 1.631 – 1.642
Birefringenceδ = 0.037
2V angleMeasured: 50° to 63°, Calculated: 42° to 60°
Dispersionr > v weak to very strong
References[1][2][3]

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.

Occurrence

It was first described in 1828 at Mount 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.

See also

References

  1. Handbook of Mineralogy
  2. 2.0 2.1 Mindat w/ localities
  3. 3.0 3.1 Webmineral
  4. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode2021MinM...85..291W. 

External links