Thanks everyone! Yeah, it is Prickly Pear Skeleton, or whatever you want to call it. I like to call it Cactus Guts!!
My technique for harvesting and cleaning is pretty simple really. Go find the dead, dry pads. BE CAREFUL! the thorns are barbed and really hurt when you get stabbed, and No gloves i have found will stop them, not even leather. Once you have your pads, you gotta "skin" them. This is an easy process as the skins are usually dried up and falling off already. Then you seperate all the bones (They will be in layers.. Lots and Lots of layers), and wash them. I use my shower to wash them so i can have warm water. The shower head pushes the dirt out without being too mean to the bones themselves. Then you just gotta let em dry. Cut em up, stuff your mold full and cast away!! (HAHA that reminded me of Tom Hanks!!)
I did not finish the keychain with any CA or anything else for that matter. It is sort of a test to see how it stands up without finish. There isnt any cactus "sticking out" or anything like that, but if you rub the blank, you can feel slight changes in the surface. Of course a good coat of CA finish would eliminate this and make it glass smooth.