Mineralpedia Details for Calumetite
Named after the town of Calumet in Michigan, USA which is nearby the locality where the mineral was first discovered and is also near the type locality for the mineral at the Centennial mine. Calumetite is a rare mineral with additional localities in Greece, Germany, Italy, and Austria. It occurs at the type locality “in cavities and fractures in basalt, formed by the action of chlorine-bearing connate waters on copper, [with] cuprite being regarded as an intermediate product in the alteration.” Associated minerals include tremolite, quartz, epidote, copper, cuprite, atacamite, buttgenbachite, malachite, paratacamite, and anthonyite.
Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/calumetite.pdf
Calumetite from Centennial mine, Houghton Co., Michigan, United States
Fine deep to light green scales on Copper.