Rutile is a titanium oxide mineral (TiO2). It's an important titanium ore mineral. Its most common crystal form is long, striated needles (acicular crystals). Rutile has an intense submetallic luster, a pale yellow to yellowish-brown to red to almost black color, and is fairly hard (H=6.5). Many twinned crystals have a bent or kinked appearance ("elbow twins").
Rutile occurs in igneous, sedimentary, and metamorphic rocks. Its most frequent occurrences are: 1) long, slender needles within quartz crystals (rutilated quartz); and 2) placer beach sands.
Rutile (~6.25 mm across at its widest) - a nice, dark reddish-colored elbow twin from Diamantina, Minas Gerais State, Brazil.
Rutile (pale needles) in quartz (rutilated quartz) (above & below; above: 4.9 cm across; below: field of view ~1.4 cm across).
Rutile from Graves Mountain, Lincoln County, Georgia, USA.