Magnetite, zircon, apatite, ilmenite, biotite, and garnet are common accessory minerals. Zircon, apatite, titanite, magnetite, ilmenite, and sulfides occur as accessory minerals. Minerals that typically form nodules include calcite, chert, apatite (phosphorite), anhydrite, and pyrite. Other minor inclusions are sphene, apatite, rutile, zircon, and sphalerite. Shales may also contain concretions consisting of pyrite, apatite, or various carbonate minerals. Associated minerals include zircon, aegirine, apatite, perovskite and columbite. The accessory minerals are magnetite, ilmenite, apatite, and titanite. Hydroxyapatite is the hydroxyl endmember of the complex apatite group. Later, samples of the bone apatite (hydroxyapatite) fraction from mammoth bones were radiocarbon dated. These phases can include olivine, pyroxene, Fe-Ti oxides, and/or apatite. The mottled anorthosite is composed of traces of quartz, titanite and apatite minerals. Turquoise may also pseudomorphously replace feldspar, apatite, other minerals, or even fossils. Phenocrysts in Hekla's lava can contain plagioclase, pyroxene, titanomagnetite, olivine, and apatite. The veins commonly contain tourmaline, topaz, fluorite, apatite, wolframite, molybdenite, and arsenopyrite. Associated mineral phases include&colon; corundum, apatite, serpentine, and talc.