RUTILE
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.