Swallowtail gypsum

Twinning is common in gypsum crystals which often results in beautiful swallowtail habit.

I saw very nice exposure of swallowtail gypsum crystals in Cyprus. The crystals are several meters long and they all seem to be twinned.

These crystals formed in a shallow hypersaline lagoon in the Messinian (the last stage of the Miocene) about 6 million years ago. I have also written about laminated gypsum that is exposed nearby and formed roughly at the same time but probably in somewhat deeper water.

http://picasaweb.google.com/107509377372007544953/Cyprus#5736496868746129042
Twinned gypsum crystals (selenite) in Cyprus near Elediou. I know some of you might be worried about the hammer but I can assure you that I used it for scale only. I always carry it in my backpack when geologising and use it more often for scale (if pen is too small) than for smashing rocks. I would not consider destroying an exposure as beautiful as this and I very rarely attack outcrops at all. However, I do collect and often smash loose rocks.
http://picasaweb.google.com/107509377372007544953/Cyprus#5736496870958169154