There are several interest groups on facebook and there's nothing secret about them. I'll list a few here and you will be able to find more going from the suggestions that come up when you join these:
First CABS AND SLABS,
https://www.facebook.com/groups/539242229527605/
A big group with lapidary enthousiasts and professionals from all over the world, but mainly Americans. They host an auction on Friday, a sale Saturday and a give-away on Sunday. The auction is run by the admins and they select a few members each week to offer items for auction. You can contact them prior to let them know that you have material that you'd be interested in auctioning of, but they do want to see you being active (post your work) for a while first.
You can post items to show of on all days, but only on Saturday can you outright post 'for sale' posts. The rest of the week you can add a line like "PM for more info" if you are willing to part with your treasure, but don't outright state that it's for sale. It's a tightly run group and they like to keep from getting chaotic. It is my favorite group; the knowledge there is second to none and all members are enthousiasts and show of some fantastic work.
They run a spin off for jewelry artisans that want to show what they did with the material bought in this group.
They don't have any faceters there (yet), but I think they would be very welcome.
Then there's Australian Crystals and Minerals:
https://www.facebook.com/groups/australiancrystals/
They don't want lapidary work posted, but it has an incredible array of knowledgeable memberson anything Australian. They will help identify, know about good stuff and there are incredible examples of our mineral wealth posted there. They have a separate 'for sale'page here:
https://www.facebook.com/groups/ACMsales/
(Oh, and no metaphysical rubbish either, they focus on facts, not magic.)
Then there's
https://www.facebook.com/groups/204479096324062/, Minerals for auction and sale
It is not the most active group, but you can sell there and see what others have for sale. The main focus seems to be on mineral specimens, but rocks and rough and cut stones are also allowed. You will find some quality faceting material from Pakistan and the sellers are generally vetted so they can be trusted. Just keep in mind that this is the internet and it just might happen that you may be the first person to deal with a certain seller, so no info is available yet. Report problems with sellers (and buyers!) to the admins immediately (this goes for all groups by the way). They will try and help to reach a solution, and remove dodgy people swiftly if it turns sour.
There's a group that documents and archives all the dodgy deals done where there was no resolution found. It is a good idea to check your buyer or seller against this list,but I can't remember the link. If I find it again, I'll post it.
I have more groups I'm a member of, but these offer by far the most quality.
I haven't seen any faceted materials in any of these groups, so I think you'd be quite the sensation!