I have been collecting buttons for over 20 years. I have a pretty decent collection. I am going to be selling off a ton that are vintage, but not very collectable. Pretty much everything has been covered, MOP and Glass are cold to the touch, and bakelite can be tested with the Dow, or Pin test. I did have one bakelite that I swore was glass, but when I did the burn test I turned out that it was bakelite. Then there are the old celluloid, and lucite, bone and ivory, metals and uniform... Some of these can be a little tricky to identify. My personal favorites are the old hand carved pearl buttons, and I just love the old pink moonglow glass buttons. Here is a good link for anyone wanting info to identify older vintage buttons, esp glass.
http://vintagebuttons.net/educational.html Click on the photos, and that will take you to the type of button listed. Keep in mind these are very collectable types, but will give you something to use for comparison.
Good Luck with your listings.
Laura