Here’s a new hardness testing technique.
   I’m in Tucson at one of those dealers that puts their gems in little plastic trays.  You know the ones I’m talking about.  I see a parcel of Tsavorite that looks interesting: we like to buy cheap abraded material and recut if we can get it at a bargain.  One of the largest pieces in the parcel is heavily abraded but looks clean so it attracts my attention as a potential recut.  It seems way more abraded than the rest so I ask the owner whether he’s mixed this lot with newer lots and he says “no”.  He tells me this is a parcel he bought about 6 months ago and he’s been selling from it since.  I told him that in that case, the big one is likely glass or possibly Diopside.  He disagrees but trusts my judgement enough to check it out.  It turns out it was green glass.  It didn’t sell because it was so abraded and it had probably been in the lot since before he bought it.  There was no deception intended so we parted on good terms with his biggest Tsavorite now relegated to the trash bin.
   This is not a hardness testing technique I would recommend, but it is a lesson to be learned.  Gems of the same hardness can and will damage each other if not carefully handled.  Gems of lower hardness can be downright abused by harder gems.  In this case the gem was glass and when ruined by abrasions probably didn’t make much difference.  But imagine if it was a Chrome Diposide.  Chrome Diopside would likely be damaged in the same manner and could have meant $100 difference in value.  Be wary of gems sold in trays like this.  Always look carefully for chips and abrasions before you purchase.