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?
Do you know the most common mineral in planet earth? Quartz? Nope. Feldspar? Nope. Ah, you say: All that limestone, the answer must be calcite. Wrong again. OK, you think it is a trick question. Maybe it is ice with all the polar ice sheets. Nice try, ice is a mineral, but not correct.
What if I told you this mineral cannot be collected anywhere and that it was not officially named until last year even though it comprises ~38% of the earth by volume. Why, you might ask? How about because no one had been able to find a sample to analyze? Are you catching on?
The newly christened mineral is bridgmanite. For a long time, scientists have known that a significant portion of the earth’s lower mantle is a very dense magnesium-iron silicate mineral. However, lacking a sample they could not characterize the material and without crystal structure information it could not be properly studied and named.
Article I wrote for the Dec. 2014 WCGMC News
The Hope diamond is one of the most recognized and well known jewels in the world. At 45.52 carats (9.104 grams), the 1” by ¾” pear-shaped blue jewel is currently valued at more than 200 million dollars. From its undocumented discovery in India in the 17th century (or before), the diamond has seen owners in India, France, and Britain before coming to the United States early in the 20th century. It has been re-faceted on several occasions to improve quality and luster. The gem has resided in the Smithsonian Museum of Natural History since 1958, when Harry Winston, a jeweler from New York City, donated the famous gem with the hopes it would stimulate further donations. It did and the National Gem Gallery at the Smithsonian is a must visit for anyone trekking to Washington D.C.
Article I wrote for Dec. 2014 WCGMC News
The Salt of the Earth
This month we will talk about a local mineral location, but not a collector site. It is in our backyard. Well perhaps more appropriately, it is in our cellar. The rocks and the minerals it contains do not crop out, but they are everywhere. And none of us could live without them.
OK, admit it, you have not heard of the Hampton Corners Mine? But maybe you know where the largest salt mine in the United States is located? Yes, it is the Hampton Corners Mine, and it is located just south of Rochester, NY. You drive by it just outside Mt. Morris if you are headed to, or from, Rochester on 390. For a moment when you drive past you may even wonder what they do in that strange looking building just east of the highway.
The Hampton Corners salt mine was opened by American Rock Salt in 1998 to replace the flooded Retsof Mine of Livingston County just 6 miles north. After over 100 years of continuous mining, the catastrophic 1994 flooding event in the Retsof Mine left the region with a demand for low cost road salt, but no local source. American Rock Salt stepped into that void as local businessmen purchased the property near Mt. Morris and established a new mine. In fact they established the only new salt mine in the United States in the last 40 years.
Winter is coming to upstate New York so I decided to take us to the desert for this month’s column, specifically to the large, generally flat dry lake beds of Death Valley National Park in California. For decades scientists have observed large rocks strewn about the playa surface and speculated about how they got there. Often they are found with long, sometimes curved tracks suggesting movement across the desert surface.
In the past, many theories were proposed to explain how rocks, some as heavy as 700 pounds, could slide or sail across the dry lake bed creating a furrow or trail in their wake. Hurricane force winds and muddy playa surfaces were suggested. Slick algal mats present during rare wet periods and thick ice accumulations were also proposed, but experiments and models developed with these ideas could not duplicate the phenomena. Furthermore, it did not seem reasonable that roving herds of pronghorn antelope had entertained themselves by pushing stones around while no one was watching. Besides there were no hoof prints!
Mineral collectors know about the fine magnetite, sphalerite, hexagonite, chrome tremolite, lazulite, etc. that have come from the various mines in the Balmat-Edwards Zinc District of upstate New York. Mineralogists have studied the district for decades discovering new minerals like turneaureite and donpeacorite. But seldom are we offered such a wonderful opportunity to learn the geology of the district as afforded those attending the New York State Geological Symposium in Alexander Bay in October.
The opening address was delivered by William deLorraine, Chief Geologist for St Lawrence Zinc Co. in Gouverneur, NY. Bill is also the President of the St. Lawrence County Gem and Mineral Club. Continue reading
An article I wrote for the April 2014 WCGMC News
The Rochester shale comprises the upper 85’-90’ of the Middle Silurian Clinton Group in upstate New York and southern Ontario. The upper two-thirds of the unit contain numerous grey limestone beds, which can be sufficiently resistant to form outcrops, but which are poor in fossil content. The lower 20’ of the Rochester shale is notoriously susceptible to erosion such that outcrop exposure is rare. Unfortunately, it is this rapidly weathering unit at the base that contains the abundant fossil assemblage (specifically trilobites) for which the formation is famous. The best visible exposure of the full Rochester shale section is in the gorge walls of High Falls on the Genesee River. However, this section is agonizingly unapproachable for fossil collection, particularly so the lower 10-20’ of section best known for fossil diversity and abundance.
Over 200 invertebrate fossil species have been identified from the Rochester shale including corals, brachiopods, bivalves, gastropods, cephalopods and crinoids. But, it is the spectacularly preserved trilobites that have attracted collectors to the Rochester shale since James Hall first detailed their occurrence in the 1840’s. The diverse fauna combined with the fine grained shale beds and thin limestone units indicate that the Rochester shale was deposited in warm, well oxygenated marine waters of intermediate depth. But where does one find outcrop to search for fossils?
Article I wrote for the March, 2014 WCGMC News
If Time is Relative, Geologic Time is Exponentially Relative
The geologic time scale is a difficult concept for humans to appreciate. We live less than 100 years, the Vikings came to America 1000 years ago, our current calendar just passed the 2000 year mark, and Stonehenge dates almost 5000 years old. That, we say, was a long time ago. But these are mere seconds on a geologic clock. Even the final Ice Age advance that generated upstate New York’s topography and fertile soil ended a mere 12,500 years ago.
Now think about this. Dinosaurs roamed and dominated much of the planet for the entire Mesozoic Era. For over 160 million years (MY) they lived, and died until going extinct about 65 million years ago. By comparison, humans have been inhabitants for just under one million years. And all but the last 6000 years or so of that is referred to as the Stone Age, the period before metal was worked and likely before crops were cultivated.
Geology in Action, Wolf Creek Dam, Lake Cumberland, Kentucky
The construction of Wolf Creek Dam in central Kentucky began in 1941, but work was interrupted by WW2 and the dam was not completed until 1951. Potential problems with the integrity of the underlying Ordovician Leipers limestone were appreciated during construction and extensive cement was placed in a number of cave features that were known to exist before the earthen dam was built above. However, that early work proved to be insufficient in preventing seepage from Lake Cumberland through the underlying karst.