Rutili

Rutili is the Italian plural form of rutile, a mineral with the chemical composition TiO2. Rutile is one of the most important titanium-bearing minerals and a major natural source of titanium. The name derives from Latin rutilus, meaning red, referring to the typical reddish-brown color of many rutile crystals.

Rutile crystallizes in the tetragonal system and commonly forms prismatic or needle-like crystals. It has a Mohs hardness of about 6–6.5 and a specific gravity around 4.2–4.3. The mineral exhibits a high refractive index and strong birefringence, and its color ranges from colorless to brown, red, or black depending on impurities. Natural rutile often occurs as fine, acicular crystals that can be found as inclusions in other minerals or as large, well-formed crystals.

Occurrence and formation data indicate rutile appears in a variety of geological settings. It is common in igneous rocks (such as granites and pegmatites) and metamorphic rocks (including granulites and mica schists), and it is abundant in heavy mineral sands along coastlines. Rutile is frequently associated with other Ti-bearing minerals like ilmenite, as well as zircon, cassiterite, and magnetite.

Industrially, rutile is a principal source of titanium dioxide (TiO2), used widely as a white pigment in paints, plastics, coatings, and paper. It also serves as a feedstock for titanium metal production and has applications in ceramics, glass, and photocatalysis. In geology, rutile is used in U-Pb dating to determine the timing of metamorphic and tectonic events due to its capacity to incorporate uranium.

Rutili, as a term, thus encompasses rutile crystals and grains encountered in natural settings, with significance in both economic geology and geochronology.