Characteristics of opals from Simav, Turkey

F. Esenli*, I. Kumbasar, R. H. Eren, B. Uz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

The characteristics of opals with various colours found in rhyolitic volcanic rocks from Simav district (west Anatolia, Turkey) were studied by optical, X-ray, thermoanalytical and infrared-absorption methods and scanning electron microscope-energy dispersive X-ray spectrometer. Four different silica polymorphs were distinguished. These are massy opal-CT found as nodules, prismatic trydimite crystals found in geodes with opal-CT, fibrous opal-C as spherulites and authigenic microcrystalline quartz found in the voids, fractures and matrix of the rhyolites. Opal-CT which is known as "Simav's fire opal" has high water content related to its fractured and disordered microstructure. The colour variation of massy opal-CT is due to its structural states and changes in its composition. Simav's opals were precipitated from saturated siliceous solutions under low temperatures.

Original languageEnglish
Pages (from-to)97-113
Number of pages17
JournalNeues Jahrbuch fur Mineralogie, Monatshefte
Volume3
Publication statusPublished - 2001

Keywords

  • Fire opal
  • Opal-C
  • Opal-CT
  • Simav's opal
  • Turkey

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