Rutile is one of five natural forms of titanium dioxide and the most abundant. It sometimes forms like wheat straw or needles within other crystals such as quartz or topaz. Rutile has an adamantine luster and refractive index that rivals diamond but cannot compare in hardness.
Chemical composition: TiO2; Hardness: 6-6.5
Smoky is a variety of Quartz colored by trace elements built into the crystal lattice, in this case, aluminum. Irradiation of aluminum impurities within the quartz produces the grayish to brownish-black color
Quartz Chemical composition: SiO2; Hardness: 7