BOTALLACKITE FROM CORNWALL

 

I recently wrote about the mineral ettringite from the Kalahari Manganese Field that was purchased at the recent Denver Spring Show. Another micro, botallackite, that I lugged home was originally in the collection of Erich Laskowski, then acquired by Shannon Minerals (Tucson), was remounted. and then ended up as a lonely specimen in Denver.

I don’t know much about Erich Laskowski (1949-2020) except he “was a mining engineer, working principally at Bagdad, Arizona, and Hayden Hill, California. Mr. Laskowski collected minerals his entire life, assembling his collection from the 1970s to circa 2014” (Mineral Species.com). Recently vendors Mineral Species, Marin Minerals, and Mineral Classics have been liquidating his collection.

Botallackite is a hydrous copper chloride [Cu₂(OH)₃Cl] usually occurring as tiny, green (various shades) prismatic to tabular crystals that form a translucent to transparent, soft crust on a matrix or are simply scattered across the matrix. Crystals in a crust often are indistinct while the scattered crystals are more easily recognized. Perhaps the most interesting thing about botallackite is that it forms in or near marine waters as copper deposits or copper slag weathers. The sea water provides chlorine while rocks provide copper.  Most specimens on the market come from the cliffs around Cligga Head on the southwest coast of Cornwall, England, which has a mining history dating back perhaps 4000 years. Mines, shafts, and adits are scattered over the area as both copper and tin were mined by the U.K. in the 1700s-1800s and were critical components driving England’s Industrial Revolution. The copper and tin minerals were hosted in veins and replacement wall rock of Devonian metasedimentary rocks. Hydrothermal fluids probably emulated from the Permian Land’s End Pluton (mostly granite) rock. My tiny specimen came from an unnamed mine on Cligga Head on the Cornwall Coast near Perranporth.

Cligga Head on the Cornwall Coast near Perranporth. Notice the numerous mine openings from near the beach (center left) and immediate front. One of the main entrances to the Cligga Head Mine was on top of the plateau. Major mineral commodities were tin, copper, and tungsten. I hope to visit mining relics on my upcoming trip to Cornwall. The photo is courtesy of cornwalls.co.uk.

    

In the above photomicrograph some botallackite crystals reflect light (and appear shiny) while others (with arrows) are pale green and appear translucent to transparent. The blue patches are indistinct crystals of connellite [Cu₁₉(SO₄)(OH)₃₂Cl₄ · 3H₂O].  Maximum width (bottom) FOV ~6 mm.