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Apophyllite on Prehnite

UNB-2017-0151Minerals » Silicates » Phyllosilicates

Description

Slightly off-white euhedral Apophyllite crystals on Prehnite. Apophyllite (KCa4Si8O20(F,OH) x 8H2O) can be either colourless, white, grey, greenish, yellowish or reddish in colour. Lustre is vitreous and pearly along the cleavage. Streak is white and hardness is 4 1/2 to 5. Cleavage is perfect in one direction. Apophyllite usually occurs as cube-like or tabular crystals. Prehnite (Ca2Al2Si3O10(OH)2) can be light green, oil-green, grey, white or colourless with a vitreous or waxy lustre. Streak is colourless and hardness is 6 to 6 1/2. Cleavage is distinct in one direction. Prehnite usually occurs as botryoidal masses but can also be stalactitic and radial in form.

Specifications

Object nameApophyllite on Prehnite
IDUNB-2017-0151
Legal statusPermanent collection
CategoryMineral
Classification
Mineral group:
Silicates
Sub-group:
Phyllosilicates
Composition
  • (Al,Fe2+,Fe3+Li,Mg,Mn,Ni)5−6(Al,Fe3+,Si)4(O,OH)18
  • K(Fe,Mg)3AlSi3O10(OH)2
  • (Mg,Fe2+)5Al(Si3Al)O10(OH)8
  • Various (e.g., Muscovite - KAl2(AlSi3O10)(OH)2)
  • Al2Si2O5(OH)4
  • K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2
  • Na2AlSi3O8·H2O
  • LiAlSi4O10
  • NaAl2(AlSi3O10)(OH)2
  • D3[Si2O5](OH)4
  • Mg3(Si2O5)(OH)4
  • KAl2(AlSi3O10)(F,OH)2
OriginUnknown
Pieces1
PartialNo
Measurements
  • 9cm x 5cm x 4cm

Publications

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