I visited Holts for the first time last week with my jewellery class. I had probably been too intimidated to go in before, but this time we just said we were students and they were very nice about it, showing us stones even though we were not going to be buying (yet...).
I asked to see what they had in prehnite, as I love the colour, and they showed me some cabochons that were very high domed. Beautiful, £55 each. Hmm.
I realised I had no idea what that cut is called (and was too shocked by the price to ask at Holts) but after a bit of research it turns out they were bullet cut.
Here is an example of such a cut - I really like it but apparently it's not the easiest to set, so I shall wait until I have a bit more experience before buying any...
Here is a link to how they can look in jewellery - a lovely ring I found on Etsy and made by Jesse Danger