Astrophyllite is a very-rare, brown to golden-yellow hydrous potassium iron titanium silicate mineral.
Heavy, soft and fragile, astrophyllite typically forms as bladed, radiating stellate aggregates. It is this crystal habit that gives astrophyllite its name, from the Greek words astron meaning "star" and phyllon meaning "leaf".
Owing to its limited availability and high cost, astrophyllite is seldom seen in an ornamental capacity. It is sometimes used in jewellery where it is fashioned into cabochons.
Found in cavities and fissures in unusual felsic igneous rocks, astrophyllite is associated with feldspar, mica, titanite, zircon, nepheline, and aegirine. It was first discovered in 1854 at its type locality; Laven Island, Norway. Astrophyllite is found in a few scarce, remote localities: Mont-Saint-Hilaire, Quebec, Canada; Pikes Peak, Colorado, USA; Narsarsuk and Kangerdluarsuk, Greenland; Brevig, Norway; and the Kola Peninsula, Russia.