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Amethyst (Cactus Quartz)

UNB-2017-0246Minerals » Tectosilicates

Description

Sample of long, prismatic euhedral Amethyst crystals that is terminated by double rhombohedron. Secondary Amethyst crystals overgrown on the large prismatic Amethyst. The secondary crystals are short, euhedral prismatic crystals that are terminated double rhombohedron. Vitreous lustre. Average secondary growth crystal size: 0.3 cm x 0.2 cm x 0.25 cm. Quartz (SiO2) can have a large variety of colours and when it is purple it is known as Amethyst. Lustre can be vitreous or greasy and streak is white. Hardness is 7. Quartz can be long or short prismatic crystals that are terminated by double rhombohedrons and have striations crosswise. Quartz can also be massive, granular, or disseminated. Cactus Quartz is the secondary generation of Quartz crystals.

Specifications

Object nameAmethyst (Cactus Quartz)
IDUNB-2017-0246
Legal statusPermanent collection
CategoryMineral
Classification
Mineral group:
Tectosilicates
Composition
  • CaB2Si2O8(OH,F)2
  • (Ca,Na2,K2)Al2Si4O12•6H2O
  • (Ca,Na)AlSi2O8
  • (Na2,K2)Al2Si4O12•2H2O
  • (Na,Ca)4(Al,Na)3Si9O24(Cl,CO3)2
  • (MAlO2)(SiO 2)x(H2O)y
  • (Na,K)AlSiO4
  • Na2Al2Si3O10·2H2O
  • KAlSi3O8
  • Na2Ca2Al6Si9O30·8H2O
  • K(AlSi2O6)
  • CaAl2Si4O12·4H2O
  • Pectolite NaCa2Si3O8(OH)2H2O with trace amounts of copper
  • (Ca,Na)(Al,Si)4O8
  • SiO2 with water inclusion
  • (Na,Ca)4-8Al6Si6(O,S)24(Cl,SO4)1-2
  • Na8(Al6Si6O24)Cl2
  • CaAl2Si3O10·3H2O
  • SiO2
  • (Cs,Na)2Al2Si4O12·2H2O
  • (Na, Ca)(Al, Si)AlSi2O8
  • KAlSi3O8
  • (Na,K)AlSi3O8
  • (Na,K)AlSi3O8
  • CaAl2Si2O8
  • SiO2
Age
Eon:
Phanerozoic
Era:
Mesozoic
Period:
Cretaceous
Numeric age145 Mya
OriginUnknown
Pieces1
PartialNo
Measurements
  • 1.2cm x 5.7cm x 1.8cm

Publications

  • Chesterman, C.W. 1979. Audubon Society, Field Guide to North American Rocks and Minerals. Knopf.