New Mexico Mineral Symposium — Abstracts

As man became interested in minerals and curious about them he gathered and shared information. A major publication by Dr. Victor Goldschmidt, Atlas der Krystallformen (1917) depicted several occurrences of quartz crystals showing the basal or c face. Of the publications that Goldschmidt cited as sources of his information, I have only been able to locate one in the library of the Technische Universitat Berlin, a paper by Maskelyne (1877). This paper describes five amethyst quartz crystals showing the c face. A detailed study of the faces on these crystals leads to the conclusion that they all are fourling twins. All were crystals showing no prism faces and suspected of occurring in a geode.

In Les mineraux de la Belgique (Buttgenbach 1938), in the chapter on quartz, page 208, the author mentions that in the collection of the University of Liege there is a crystal terminated with the basal plane (0001). This is specimen number 11026 and is still in the collection. The specimen is from Nil-Saint-Vincent.

I have obtained four macro-size crystals showing the basal pinacoid: one amethyst from Bolivia, one amethyst from the Four Peaks mine in Arizona, one smoky crystal from Hidden, North Carolina, and one from the CF&I marble quarry near Monarch Pass, Colorado.

In the micromount collection of the Denver Museum of Nature and Science there are 14 quartz crystals showing the c face. Several occurred in rhyolites, several are from the Amethyst mine at Creede, Colorado, several are from the Olsen ranch, Park County, Montana, and several are from the Ellis Emerald mine, North Carolina. These crystals showing the basal face were popular with micromount collectors, and most museums that have micromount collections will have some in their collections.