Astrophyllite is a very rare, brown to golden-yellow hydrous potassium iron titanium silicate mineral.

Its great submetallic gleam and darkness contrast sharply with the light (felsic) matrix the mineral is regularly found within.

As the crystals themselves possess perfect cleavage, they are typically left in situ, the entire aggregate often cut into slabs and polished.

Found in cavities and fissures in unusual felsic igneous rocks, astrophyllite is associated with feldspar, mica, titanite, zircon, nepheline, and aegirine.

Astrophyllite is found in a few scarce, remote localities: Mont-Saint-Hilaire, Quebec, Canada; Pikes Peak, Colorado, US; Narsarsuk and Kangerdluarsuk, Greenland; Brevig, Norway; and the Kola Peninsula, Russia.