This is a 63ct fossil snail turritella agate cabochon, in the shape of a cushion. This one is good for those interested in collecting the many forms of agate, jasper, or as in this case, "other" minerals. One can also glue on "bails", or have the piece drilled to accept a bail with posts - either approach will let you turn this sample into a fine pendant.
Turritella is a genus of medium-sized sea snails. They have tightly coiled shells, whose overall shape is basically that of an elongated cone. These ones are naturally fossilized. The name Turritella comes from the Latin word turritus meaning "turreted" or "towered" and the diminutive suffix -ella. (Thank you Wikipedia for this information.)
Although this is a cab, you can also glue on "bails", or have the piece drilled to accept a pinch bail. Either approach will let you turn this sample into a fine pendant.