A number of years ago i was searching at a drive in theater.about a quarter inch under the ground i found a almost black Lady's four prong ring that had apparently been stepped on.I thought well it being silver the stone could have not been valuable,and went on to other targets.About two months later i was cleaning the ring and discovered i had found my one and only platinum ring.I went back to the theater and scratched around for the stone then i went back several times at night and tried the u.v. sunglasses trick.well i never found the stone,but the time i find a mounting i will take time to look for the stone.My jeweler said that whatever the stone was it was probably to karats judging by the spacing between the prongs.