Rutilated quartz is a variety of quartz containing acicular inclusions. These needle-like inclusions are of rutile, which is a mineral containing titanium dioxide and often contains iron oxide, in various quantities. The lower the iron oxide content, the darker the strands of rutile will be, with some even appearing to be dark blue/ black. These varieties will be known as 'black rutilated quartz' or 'blue rutilated quartz'.
