A gemmy clear blue-green tourmaline "rod". Tourmaline comes in many colours and is an October birthstone (along with opal). Good tourmaline rod crystals have a kind of rounded triangle cross-section, which you can see across the top of this specimen. This one is mounted in a gold coloured base.
3/16 inch (0.5 cm) diameter base and just under 3/8 inch (0.95 cm) tall.