This is a totally natural stone called Starulite in Shist , sometimes called fairy crosses ! The brown starulite crystals formed in the white shist and sometimes , rarely, form a cross. It is found in Russia. It is 1 3/4" from the top of the bail to the bottom, 1" across , and 1/4" thick. I hand carved it in wax and had it cast in sterling silver. It is on a multi strand chain of black cord and ribbon that is 16" long with an extra section of chain 1 3/4" long for longer adjustment. i've included a photo of a specimen of this kind of rock.