Found this in Folkestone Kent whilst looking for fossils. It has broken as you can see.
Is it crystal?
If so what kind?
Superficially, it does look like gypsum (rather like the grey form very common here in Cyprus).
There are a few characters that can be used to distinguish gypsum from calcite, but the easiest to use is scratch hardness. Try to scratch it with your fingernail (hardness 2.5), using a solid-looking part of your specimen(s). If you can scratch it, it is gypsum (hardness 2), if not it is may be calcite (hardness 3) (there are other possibilities, such as barite, though you'd know that because of its greater density).
- Gypsum properties - http://www.galleries.com/Gypsum
- Calcite properties - http://www.galleries.com/Calcite
- all sorts of interesting stuff abotu gypsum - http://answers.yahoo.com/question/index?qid=20070213132837AA2RpXE
- Mohs scale of scratch hardness - http://chemistry.about.com/od/geochemistry/a/mohsscale.htm
I can scratch it so looks like its gypsum, we found it in the clay down at Folkestone there are some very clear parts in the crystal I dont know if the grey is clay its very delicate.
Thank you for the information links at the end of that i will have a look through the sites.
Jolly good Amy.
The gypsum at Folkestone comes from the gault clay.
You're not the first to find gypsum crystals on the shore at Folkestone:
On this page, there's a nice photo entitled "Right: A large gypsum crystal, found loose on the foreshore."
That one happens to be very clear.
There are a bunch more photos of gypsum here
...showing the considerable range of appearances.
...underlining the fact that appearance can be an unreliable character for identification,
and by implication, making the hardness test that much more valuable in the case of gypsum.
Note the term selenite in connection with gypsum. This is a clear, well-crystallised form of the mineral.
Term refers to the moon, not to the element selenium. There are various selenite compunds, eg. sodium selenite. These are also unrelated to the mineral selenite.