Thanks and I did just that. One of the gem mines down the road from me proclaimed it to be Helidor. The frosty look was due to sand washing in the creek. Interesting note, my creek is fed off the larger one through their mine! Think I am getting the salting run off they use to do...
If the mine is 'salted', perhaps.
The sharp corners suggest it may not have been in the water for to long, nor travelled very far. Doupt it's the work of sand.