Home > Laskowski Ⅲ – July 6 > MS1865 Groutite on petrified wood

Groutite on petrified wood - Sold


Groutite is a manganese oxide hydroxide. Gruner (1947) named the mineral after Frank F. Grout (1880-1958), petrologist at the University of Minnesota, Minneapolis.

Collectors noticed unusual black crystals in some Arizona petrified wood logs since the 1950s. The earliest specimens carry designations of "stibnite", but by the time of the 1997 Mineralogy of Arizona, its identity as groutite had been resolved. This specimen is an angular fragment of purple-red petrified wood hosting black groutite needles to 1.5 mm. From the collection of E.R. Laskowski (1949-2020), a mining engineer who retired to Tucson, Arizona.