Yes, you are correct, I had included both your rare zinc sulfite mineral in the beginning when I was discussing how it was created. (Usually in a highly humid or wet acidic environment at normal pressures.)
Then I expanded the discussion to include your evidence of Bleaching of the Iron Magnesium Dioxide Shist with the crystal filiments growing on the surface, (...looking a bit like the grain structure in an iron meteroite.) It was this sample that appeared to require the hot acidic CO2 rich environment under pressure.)
The main point I was trying to illicit was, it would appear your embedded statement relating to the original mineral being due to CO2 bearing rain did not seem to be very well supported. When in effect it likely had to of formed in either a hydrogen sulfide or sulfuric acid rich atmosphere.
Could you please help me in understanding why that statement was supported by the evidence, I simply do not see it...
Is this the image you are referring to Dave? ...."Iron Magnesium Dioxide Shist with the crystal filiments growing on the surface, (...looking a bit like the grain structure in an iron meteroite.)"
This is lower Silurian mudstone. In this area it is normally slate-grey. Here is an example, mined at depth and cut and polished, showing fault-breccia of grey mudstone cemented by quartz and zinc sulphide:
This is unoxidised: weathering had not penetrated to that depth. Now consider this:
You can immediately see that only local cores of grey remain in the mudstone fragment; the remainder has been bleached to buff shades. The white crystalline mineral is the lead carbonate, cerussite, which is accompanied by iron oxides. The primary ore found at depth at this mine was shattered mudstone, cemented by quartz, sphalerite (zinc sulphide) and galena (lead sulphide). The iron came from the sphalerite - it always contains a certain amount. The zinc itself simply ended up in the groundwater - it is very soluble, but the relatively insoluble lead leached from the galena combined readily with carbonic acid to form the carbonate.
In very acidic environments, these reactions do not occur the same way. The classic example in Wales is Parys Mountain on Anglesey, a massive sulphide deposit in which galena was common but pyrite was abundant: its weathering formed so much sulphuric acid that the oxidation assemblage consisted of iron oxides and large amounts of lead sulphate - Anglesite - named after the place at which it was first described in the 1830s. However, Parys Mountain is unusual in that respect and down here in Central Wales, pyrite is relatively localised and often only present in traces, so that in the oxidation assemblages carbonates dominate over sulphates - completely so in the deep-weathered stuff that is generally thought to have formed in the tropical conditions of the early Cenozoic, as in the cerussite-rich specimen illustrated above, which would not have formed in a very acidic, sulphuric acid-dominated geochemical environment.
Hope that makes sense! More interesting than discussing Heartland and their anti-science arm-waving in any case!
Cheers - John