Silicate mineral
Pectolite Category Inosilicate mineral Formula (repeating unit) NaCa2 Si3 O8 (OH) IMA symbol Pct[ 1] Crystal system Triclinic Crystal class Pinacoidal (1 ) (same H-M symbol ) Space group P 1 Unit cell a = 7.99 Å, b = 7.03 Å, 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 [ 2] [ 3] [ 4]
Pectolite is a white to gray mineral, Na Ca 2 Si 3 O 8 (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. There is also a whitish form of the mineral from Alaska that is sometimes marketed as 'Alaska jade'.
Occurrence
Larimar It was first described in 1828 at Mount Baldo, Trento Province, Italy , and named from the Greek pektos – "compacted" and lithos – "stone".[ 3] [ 4]
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
External links
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