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Notes from Railay

This note was posted to the Titanium Bolting FB Group 12 January 2020

The “sulphur” crag story continues. Here we see calcium sulphate crystals deposited on the surface of the rock at Defile Exit, Railay. I hypothesise that this material is deposited as a result of bio/geochemical processes occurring at the rock surface due to the agency of sulphur oxidising bacteria.

I’ve come across small amounts of sulphate efflorescence from seepage at other “sulphur” crags across the world, but never in such abundance and purity as we see here.

The sea is a few metres distant, the sulphate levels extreme, knowing what we now know, it is no surprise this crags eats 304SS. It was rebolted in titanium maybe 6 years ago, and those new bolts look perfect.

For the benefit of Doubting Thomas (he’s very right to doubt) my identification of calcium sulphate is as follows –

  • crystal form
  • scratch with finger nail
  • dissolve in 1M HCl
  • dense white precipitate with BaCl2


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