Please create a category in the collectable, rocks and minerals, for; "fine mineral specimens" this is the only way that collectors will have a chance to find real specimens rather than look through the long lists of unrelated items, eBay has promised to do the same.
I have encouraged many of my regular eBay clients to look at your site but they refuse to spend their time looking through myriads of unrelated polished stones and carvings to see few chunks of amethyst.
I would list lots of my items if you do so and so would many others.