They as much diamond as... the 'Herkimer Diamonds' of the US or elsewhere - i.e. rock crystal, nothing else.

There's lots of 'jokes' about gems and jewelry, and it sounds like you have just heard a silly one... that these things have diamonds in the mix.

Try the gemology forum (www.gemology.com) - there were a few questions about the same material. These things are also called 'desert diamonds'.

However, there this is quartz with a story: not exactly a precious object, but definitely a conversation piece by all means.

My 2c. When expert opinion is needed about a precious stone, gemological laboratories and appraisers are there to do the job.