Mineralpedia Details for Alamosite
Named for the type locality at Alamos in the Alamos Municipality in Sonora, Mexico. Alamosite is a rare mineral that occurs in additional localities in the United States, Namibia, and Sweden. It occurs as a secondary mineral in oxidized lead-bearing base metal deposits in association with wulfenite, leadhillite, cerussite, anglesite, melanotekite, fleischerite, kegelite, hematite, diaboleite, phosgenite, willemite, shattuckite, and wickenburgite.
Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/alamosite.pdf
Alamosite from Tsumeb mine, Tsumeb, Namibia
A single, 1.7cm single crystal. It looks terminated but it is not. It's an excellent crystal group.