Astrophyllite is a very rare, brown to golden-yellow mineral. Though occasionally used in the gem/jewelry as cabochons, it is of primary interest to collectors because of its color, crystal forms and sub-metallic luster. Additionally, this same sub-metallic luster along with its darker yellow and brown colors contrasts beautifully with the usual felsic matrix (an igneous rock that is rich in feldspar and quartz and lighter in color), making it especially appealing to collectors.
The crystal system for Astrophyllite is triclinic, typically forming as bladed, stellate aggregates (“Stellate: Long thin crystals radiating outwards in all directions, like a starburst or in a circular pattern.”). This very crystal habit is what gives Astrophyllite its name, from the Greed words astron meaning “star” and phyllon meaning “leaf.”
This uncommon mineral is found in limited localities, including Canada, Greenland, Norway and Russia.