A gemmy green tourmaline "rod" with a brighter green at the top. The bright green may be due to internal flaws, I'm not sure. 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 in the second photo. This one is discreetly mounted on a polished black onyx base.
1/4 inch (0.6 cm) diameter base and just under 3/8 inch (0.95 cm) tall.