Perhaps you have heard of the latest collecting craze in the Upper Peninsula of Michigan? Beach collectors who have generally restricted their collecting to agates, amygdaloidal basalt, and perhaps an occasional greenstone are now returning to the beach after dark with a long wave UV light source. They are finding beach rocks that are bright yellow when subjected to a 365 nanometer long wave light source. Apparently there are some beaches where these stones are relatively common.
For the second consecutive year, members of Wayne County Gem and Mineral Club joined with the Niagara Peninsula Geological Society for a several day trip to mineral sites in Ontario. We thank Ashley Pollock for organizing the trip and I thank Ashley for writing this short summary of one of the sites we visited and allowing me to publish it in the September, 2017 WCGMC newsletter and also this this blog.
It rained and then it stopped and then it rained again as we drove north to start our week long summer collecting trip. But when we met our Wayne County Club friends at our first collecting stop along the French River south of Sudbury, the clouds had parted and the week of fun began.
The Rutter Pluton is a nepheline-syenite intrusion within/ straddling the border of the Grenville Front Tectonic Zone (GFTZ) of the Grenville Province. The 10 km long, 2 km wide igneous body is dated at 975 million years. Like much of the Precambrian terrain in Ontario, the igneous rocks have been metamorphosed to a gneissic texture. Mineralogically, the pluton consists of nepheline, albite (plagioclase feldspar), potassium-feldspar, and biotite mica. Quartz is absent.
In late June, Wayne County Gem and Mineral Club visited St. Lawrence County. One stop on the three day field trip was at the Valentine Mine in Harrisville where the quarry/mine operators, Gouverneur Talc Co., graciously permitted us our annual visit. Naturally all were drawn to the bright blue calcite and the brilliantly white wollastonite (the site’s economic resource), but there is another interesting rock to be collected there. Bright orange and green unakite can also be found.
The door prizes at the June meeting of the Wayne County Gem and Mineral Club consisted of a bucket of miscellaneous unpolished slabs from the club collection. Linda Schmidtgall had scoured the club collection and accumulated a wide variety of colorful and unique pieces. She set them in water for folks to make their selection. When my number was called I picked out a unique volcanic rock slab. It was an end cut, which meant one surface was raw.
Published in the July 2015 WCGMC Newsletter
I have a confession to make. Yes, I admit it, for the first few decades of my adult life I collected minerals while scoffing at the notion of cutting rocks and polishing their surface to produce symmetric reflective surfaces. Cabochons, smabochons, … spheres, smears, I would say, or something to that effect. Well, since joining the Wayne County Gem and Mineral Club I have come to realize that some rocks, even some minerals, are best displayed and enjoyed after they have been carved, sliced, ground, and polished. What is more, that process can be fun and there is art involved in the creation of a polished stone. I am not a total convert, I still cherish and generally prefer natural crystalline specimens, preferably on matrix and often in association with other minerals, but I am now capable of collecting, and yes even, horrors, purchasing a polished cabochon.
OK, with that admission of past guilt, or new guilt depending on your persuasion, I decided to peruse the GemFest floor for particularly interesting pieces that had been butchered by a saw and then beautified by some process of trimming and polishing. I found several that caught my fancy. But I must warn you, beauty, color, and symmetry are not enough. The rock or mineral must tell an interesting geologic story and just like a classic mineral specimen it must have a provenance, a banded agate from somewhere just won’t make my short list no matter how beautiful it might be. So what did I find?