Well, it is time to throw in another red mercury mineral into the mix that I have yapped about in several postings. During my long-ago mineralogy class, I learned about cinnabar, orpiment, native mercury, and that was about all--at least all I can remember although my memory may be a little sketchy! In my MS-level optical mineralogy and optical petrology classes my old course notes tell me we learned about rock forming minerals. Out at Utah we had an entire year-long sequence (we were on the Quarter System) of sedimentary petrology-carbonates and sandstones mostly. So, my early knowledge of mercury was pretty sparse, and it was not until “retirement” in Colorado Springs that I started to notice the mercury minerals at the rock and mineral shows, especially in Tucson. I also read several articles about mercury in professional journals and magazines and soon I was hunting collectables.
Montroydite is a deep red to brownish red to brown mercury oxide (HgO) with a vitreous to adamantine luster and sort of a yellowish-brown streak. I hunted quite hard on my specimens for the larger bent or twisted prismatic crystals so valued by collectors; however, the crystals I noted on the specimen were very minute and perhaps ~ .1 mm in length and generally beyond the range of my microscope. What I did locate were very dark red (tough to pick up on the photomicrographs) “globs” or non-descript massive montroydite, or perhaps masses of extremely tiny crystals The specimen also contained very minute globules of silver- colored native mercury. At one time I noticed a ~1 mm globule along the edge; however, it “rolled off” before I was able to capture a photomicrograph. Many professionals tend to spray native mercury to preserve the larger globules.
My specimen was purchased from Shannon Minerals and collected from the famous Socrates Mercury Mines, Mayacmas Mining District, near Cobb, California, Sonoma County, in the Coast Ranges. The host rock for the native mercury (Hg) and cinnabar (mercury sulfide, HgS) was an Upper Jurassic serpentinite. Geologists “in the know” believe most serpentinite forms chemically by alteration, or “serpentinization,” of rocks [peridotite] that originated in the Earth’s mantle. These “ultramafic” rocks are composed dominantly of the minerals olivine and pyroxene, which are rich in magnesium and iron, thus the rocks are very dense. During serpentinization, hot water from various sources can react with the olivine and pyroxene to produce serpentine minerals (California Geological Survey, 2023). During the late Jurassic, California (current geography) was in the midst of plate collisions and geologists believe that “peridotite underlying oceanic crustal rocks [were] metamorphosed to serpentine in subduction zones… A subduction zone is an area where ocean crust rocks run into and slide underneath the edge of a continent. Because serpentine has a much lower density than peridotite, it rose toward the surface along major regional thrust faults associated with the subduction zones.
I enjoy examining these uncommon mercury minerals although trying to understand mercury and its origins leaves me in a tizzy. I have a much better understanding of the big event of the cold season, and one to celebrate—the Winter Solstice, today December 21. This is the day, in the Northern Hemisphere, when the sun is at its lowest maximum elevation in the sky. Hence, Colorado Springs experiences the shortest period of daylight, 9 hours and 27 minutes with the sun setting at 4:40 pm or perhaps ~4:00 as it disappears behind Pikes Peak (except at my house behind a treed bluff where it disappears about 1:00 pm). Of course, tomorrow we gain one second of daylight, and by the end of the year a whopping 34 seconds. YEA.
My Danish ancestors seemed to celebrate the Winter Solstice (that seemed to morph into the Christian Christmas) with numerous festivities including eating sweet delicacies like ginger cookies or pebernꝋdders, and pickled anything such as fish (mostly herring) and red cabbage. Growing up in Kansas I had several taciturn great uncles (their parents migrated from Denmark) whose only indulgence with alcohol was communion wine and Christmas glꝋgg (warmed wine with brandy and fruit). Interestingly, several pans of those ginger Danish pebernꝋdders came out of our oven this week along with Bohemian fruit and poppy seed kolaches (heritage of my spouse). Pickled herring will be available Christmas Eve. Life is good and full of calories.
Check https://adamantkitchen.com/danish-pebernodder/ for a good pebernꝋdder recipe.
REFERENCES CITED
California Geological Survey, Note 14, Serpentine: California’s state rock: https://www.conservation.ca.gov/cgs/Pages/Publications/Note_14.aspx
California Geological Survey, 2023, Note 57 SERPENTINITE AND SERPENTINE IN CALIFORNIA: https://www.conservation.ca.gov/cgs/Documents/Publications/CGS-Notes/cgs-note-57-serpentinite-and-serpentine-a11y.pdf