Clays and Clay Minerals

, Volume 11, Issue 1, pp 158–168 | Cite as

Hydrothermal Rhyolitic Alteration in the Castle Mountains, California

  • Hendrik Heystek
Symposium on Clay Mineral Transformation


X-ray diffraction, differential thermal, chemical analysis and cation exchange data indicate a progressive genesis upon hydrothermal alteration of rhyolitic materials in an extensive fault zone. Kaolinite, a Ca-Mg beidellite, mixed-layer beidellite-hydrous mica and beidellite-vermiculite clay minerals, quartz, cristobalite and feldspar commonly occur in the deposit.

Detailed studies show that the sequence of the 2:1 clay mineral alteration is beidellite-hydrous mica mixed-layer → beidellite-vermiculite mixed-layer → beidellite. This mineralogical change parallels a progressive decrease in the layer charge and amount of fixed K+ present and an increase in exchangeable Ca+ and Mg+ respectively.


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Copyright information

© The Clay Minerals Society 1962

Authors and Affiliations

  • Hendrik Heystek
    • 1
    • 2
  1. 1.International Pipe and Ceramics Corp.USA
  2. 2.Los Angeles 39USA

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