Rutilated quartz is a variety of quartz which contains needle-like inclusions of the titanium oxide mineral rutile. These inclusions range in colour from gold, to silver, copper-red, or black, and can be illuminated under the light to spectacular effect. Sometimes the inclusions are dark enough to make the quartz appear nearly opaque, and sometimes they are distributed much more sparsely. The inclusions range from thin, sparse, and parallel, to thick, dense, and criss-crossed. The pattern of rutile inclusions in each rutilated quartz stone makes it completely unique.
Natural rutile may contain up to 10% iron and significant amounts of niobium and tantalum, accounting for the reddish tone of some of the inclusions – indeed, rutile derives its name from the Latin ‘rutilus’, meaning ‘red’. When the iron content is lower, it may appear darker, or even black in colour.
The Gemological Atelier by Harald Gemstone Sales and Solutions