This is a nice example of Mushroom Rhyolite, in the shape of a pear. This sample is good for those interested in collecting the many forms of Agate, Jasper, or sometimes other minerals, or for those interested in pendant jewelry.
Rhyolite is an extrusive igneous rock that is the volcanic equivalent of granite. Glassy versions of rhyolites include obsidian, pitchstone, perlite, and pumice. This particular sample is very attractive, resembling Jasper and having a "druzy" or crystalline section of quartz.
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.