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RE: Hiking Suikerboschfontein - Part 16 - Salt fossils indicative of Marine deposition
Hi @gavvet. Are you a geologist?
You're right. It's of marine origin.
Perhaps, it's a Volcanogenic Massive Sulfide mineral deposit. What you might have hit is a massive quartz which has interstices (ghost cubic shapes) that were once occupied by sulfides (pyrite, chalcopyrite, etc) and then removed due to oxidation (?).
Hematite is another indicator of a mineral deposit. They may have formed from the oxidation of iron-rich sulfides such as pyrite and pyrrhotite.
Hey you have just hit an ore body. Awesome! :)
Aren't those green stuff in the last picture a garnierite/epidote?
Not professionally, but well read on the subject and have done lots of field work.
This is a well studied sedimentary series. There is a good summary of the geology here:
https://en.wikipedia.org/wiki/Magaliesberg
The hematite is from circulation of iron rich ground water and subsequent ferricrete formation under sub-tropical and tropical climate cycles over the last couple of million years.
The green is also just later staining of non-precious opal or other deposits and probably also just more pronounced in this photo.
Ahhh. Wow! And the reason why it turned into a quartzite (metamorphosed sandstone) is because of the pressure applied by the weight of the Bushveld Igenous Complex - quite familiar of this on one of our subjects, and heat.
Exactly.... Closer to the intrusive layers and heat the sandstone has completely melted and re-crystallized and has grains the size of a thumbnail...