About: dbkwik:resource/RrvjD3fjOEQwnCb64NeI9A==   Sponge Permalink

An Entity of Type : dbkwik:resource/6IIoeMLPkySiK--1vpcViQ==, within Data Space : 134.155.108.49:8890 associated with source dataset(s)

AttributesValues
rdf:type
rdfs:label
  • Nontronite
rdfs:comment
  • A typical structural formula for nontronite is Ca.5(Si7Al.8Fe.2)(Fe3.5Al.4Mg.1)O20(OH)4. The dioctahedral sheet of nontronite is composed mainly of trivalent iron (Fe3+) cations, although some substitution by trivalent aluminium (Al3+) and divalent magnesium (Mg2+) does occur. The tetrahedral sheet is composed mainly of silicon (Si4+), but can have substantial (about 1 in 8) substitiution of either Fe3+ or Al3+, or combinations of these two cations. Thus, nontronite typically is characterised by having most (usually greater than 60%) of the layer charge located in the tetrahedral sheet. The layer charge is typically balanced by divalent calcium (Ca2+) or magnesium (Mg2+).
sameAs
dcterms:subject
dbkwik:ceramica/pr...iPageUsesTemplate
Category
  • Smectite - Phyllosilicate
opticalprop
  • Biaxial
mohs
  • 15(xsd:integer)
Gravity
  • 23(xsd:integer)
Name
  • Nontronite
ImageSize
  • 240(xsd:integer)
Caption
  • Nontronite from Slovakia
streak
  • Colorless
formula
  • 3(xsd:integer)
System
Color
  • Yellow, olive-green, green, orange, brown
cleavage
  • Perfect basal
habit
  • Earthy masses
refractive
  • nα = 1.530 - 1.580 nβ = 1.555 - 1.612 nγ = 1.560 - 1.615
luster
  • Earthy to dull
birefringence
  • δ = 0.030 - 0.035
abstract
  • A typical structural formula for nontronite is Ca.5(Si7Al.8Fe.2)(Fe3.5Al.4Mg.1)O20(OH)4. The dioctahedral sheet of nontronite is composed mainly of trivalent iron (Fe3+) cations, although some substitution by trivalent aluminium (Al3+) and divalent magnesium (Mg2+) does occur. The tetrahedral sheet is composed mainly of silicon (Si4+), but can have substantial (about 1 in 8) substitiution of either Fe3+ or Al3+, or combinations of these two cations. Thus, nontronite typically is characterised by having most (usually greater than 60%) of the layer charge located in the tetrahedral sheet. The layer charge is typically balanced by divalent calcium (Ca2+) or magnesium (Mg2+). Nontronite forms from the weathering of biotite and basalts, precipitation of iron and silicon rich hydrothermal fluids and in deep sea hydrothermal vents. Some evidence suggests that microorganisms may play an important role in their formation.
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