GeologyRocksHow do large chuncks of crystals from?
- Login to post a new forum topic.
Rank:
Contact:
There are actually over 900
Thu, 07/26/2012 - 20:47There are actually over 900 forms of calcite. There is one guy who tours the shows who only collects various forms of calcite, and I believe he is up to around 300 last time I spoke to him.
I suppose he is the one who would best answer your question, but I don't know his name or where he lives.
Next time he surfaces I'll try and get him to log on here.
John
“Civilisation exists by geological consent, subject to change without notice.” - Will Durant
Rank:
Contact:
When the M5 was being cut
Fri, 07/27/2012 - 06:41When the M5 was being cut through the Mendips it intersected some large solution cavities full of nail-head calcite crystals up to 6" across. These were presumed to have formed by saturated waters finding their way into the cavities and growing over a long period of time. At other locations the calcite has been deposited in veins by hydrothermal action by leaching from the surrounding limestones and large crystals can develop. As John says, there's a huge range of calcite varieties and this is reflected in the huge range of depositional situations.
Rank:
Contact:
How do large chuncks of crystals from?
Submitted by richard.k on Thu, 07/26/2012 - 16:38.https://picasaweb.google.com/116847800033838242899/CliffQuarry14022010#5760502634311892690
https://picasaweb.google.com/116847800033838242899/CliffQuarry14022010#5760502634311892690
I was recently poking around a disused quarry on the North slope of the Mendips, looking at the fossils etc when I came across some blocks of calcite crystals.
The quarry is cut into the Oxwich Head Limstone and there is a contact with the overlying dolomitic conglomerate. The crystals appear to have fallen from inside topsoil overlying the Limestone.
My question is, why are these crystals in this form rather than the dog tooth form I am more used to in this formation and how did they come to be in such large blocks and look as if they radiating from a point similar to that found in iron nodules in chalk?
Thanks for any help you can give me. I hope the pictures come out ok.
Richard K