Less important are allanite, apatite, clinopyroxene, olivine, orthopyroxene, quartz, sphene and zircon. The minerals found are quartz, mica, chlorite, albite, sphene, and graphite. Distinctive accessory minerals include&colon; fluorite, topaz, apatite, spinel, allanite, sphene and cassiterite. Amphibole, biotite, sphene, allanite, and oxides are typically more abundant. These rocks contain also iron oxides (usually titaniferous), apatite, sometimes sphene, augite, and olivine. The stability of perovskite in igneous rocks is limited by its reaction relation with sphene. Other minor inclusions are sphene, apatite, rutile, zircon, and sphalerite. Sphene is found in Half Dome Granodiorite. Sphene persists as the informal name for titanite gemstones. Biotite and hornblende frequently enclose feldspar ophitically; less commonly iron oxides and sphene do so. Owing to the quenching effect of iron, sphene exhibits no fluorescence under ultraviolet light.