Star Ruby from Burma. Star rubies and sapphires are not as rare as you may think. Star rubies and star sapphires are gemstones that exhibit a star-like phenomenon known as asterism. Star gems contain intersecting needle-like inclusions (often the mineral rutile, a mineral composed primarily of comprised of titanium dioxide) that cause the appearance of a six-rayed 'star'-shaped pattern when viewed with a single overhead light source. To cause a star, the rutile needles form in parallel and...