Astrophyllite

specimen number:
2354171

location:
St Peter's Dome, El Paso Co., Colorado, USA

description:
Thick lustrous bronze crystals of astrophyllite measuring to 4.5 x 2.2 x 0.3 cm in size throughout a quartz matrix. This is very choice for the species and locality. The specimen comes with a previous label from the collection of Jack Nieburger.

Located southwest of Colorado Springs in El Paso County, Colorado, St. Peter's Dome is a prominent geographic landmark situated within the Proterozoic Pikes Peak Batholith, specifically host to the Mount Rosa intrusive center. The local geology features alkalic granite and associated pegmatite dikes enriched in fluorine and rare titanium-, zirconium-, and rare-earth elements. Originally prospected in the late nineteenth and early twentieth centuries for gold, silver, and commercial fluorspar deposits, the area saw intermittent small-scale mining operations into the mid-twentieth century for fluorite, radioactive minerals, and specimen pegmatites. St. Peter's Dome gained international acclaim among mineral collectors as a classic American locality for astrophyllite, a rare potassium sodium iron titanium silicate that crystallizes within the pegmatite cavities as brilliant, bronze-brown to golden-yellow bladed and starburst-like radiating sprays. Although parts of the surrounding region sit on public forest lands enjoyed by casual rockhounders, field collecting remains restricted in designated watersheds and active claim areas.

Questions about this specimen?
Send an email or call us: 314-341-1811.