People come in all sizes and so do collectible rocks and minerals. There are collectors who prefer garden rocks, as big as they can carry (or even bigger). These people will do this until their yards or patios are completely covered by rocks. And then they start building piles. You know who you are! There are folks who like cabinet specimens of several inches. You need space to display these also and typically quality cabinet specimen can deplete the wallet all too quickly.
Me, I prefer mineral specimens that are called miniatures, no longer than 2” in their longest dimension. A few dozen can fit on a display shelf or in a drawer. Of course there are thumbnail collectors who specialize in specimens that can fit into a one inch cube. They even have neat little special boxes, called Perky boxes named after the collector/dealer that popularized the theme. And then there are the micromounters. These collectors can purchase much of their material less expensively and the number of available minerals seems endless, but then they require binocular microscopes and perhaps close-up camera lens to best view their prized possession.
But what about collecting minerals on thin section. Is there a place for that? OK, first off what is a thin section? According to the bible of the internet, Wikipedia tells us that a thin section is a “laboratory preparation of a rock, mineral, soil, bone, or even metal for use with a polarizing microscope”. Fine, but what is it? Let me try: a thin section is a tiny sliver of rock, typically mounted/glued onto a microscope slide that permits light to pass through all the transparent mineral phases. As it turns out if you mount a polished rock surface onto a glass microscope slide and grind/polish the surface down to 30 microns in thickness (that’s about 1/800th of an inch for the metrically challenged) then many minerals will display characteristic colors and properties upon the transmission of polarized light. In this way minerals can be identified under the microscope. Further-more their textures and how they are intergrown with each other can be used to interpret how the minerals grew and how a rock might have formed.
Published in the July WCGMC Newsletter
Admittedly, some of the Wayne County Gem and Mineral Club collecting trips are out of this world. However, that’s figurative speech as we have not yet actually figured out how to visit any true planetary bodies. No, Cobalt, Ontario does not count, not even Sudbury. But suppose we could travel to another planet to collect. What might we find? Let’s consider Mercury for starters.
Published in the June 2016 WCGMC Newsletter
All of us who live or travel in Wayne County in western New York State know it is easier to travel north-south than east-west. Most of us know that is due to the elongated hills called drumlins that cover much of the region. And we also know that those geomorphological features were formed by the continental glaciation that covered western New York with ice a mile thick until their final retreat 12,000 years ago.
BUT, did you know that until very recently, glacial geologists could not agree on exactly how these elongated parallel hills came into existence. It was known that the drumlin fields were aligned with the glacial flow and retreat, but it was unclear whether they represent debris built up progressively during glacial advance and retreat or whether they were sculpted out of older sediment from previous glacial deposits. The debate has raged for over 150 years.
It was not that long ago that Wayne County and the rest of western New York were located just south of the equator while basking in tropical temperatures. A large and shallow inland sea dominated the region with high mountains to the east and a shallow continental margin to the west. The sea was replete with life. Invertebrates dominated the sea bottom, corals and brachiopods filtered nutrients from the seawater to survive, while trilobites, cephalopods (squid), and a host of other scavenger and predator species roamed the benthic (sea bottom) region feeding on them. Numerous species of gastropods (snails) and bivalves (clams) were abundant also. The seas above were dominated by large armored fish (i.e. Dunkleosteus) and a multitude of smaller fish. It was the Devonian Period of earth’s history. It was the age of fish.
During the third week in July, seven WCGMC members spent 7 days and 6 nights collecting in Ontario. The first three days in Cobalt, Ontario are summarized here. Part 2, three days near Eganville, will be reviewed in a subsequent entry. Modified from August, 2015 WCGMC newsletter article.
From its discovery in 1903 until around 1920, Cobalt, Ontario was a hotbed of silver mining and the center of Ontario’s economic mining industry as over 10,000 inhabitants opened more than 100 mines in search of silver. Over 100 years later, and for 2 days in July, 2015, seven eager rockhounds from WCGMC followed in the old timers footsteps.
A typical scene from Cobalt: Remains from the Crown Reserve Mine in the foreground, and mine dumps from the Kerr Lake Mine across the lake.
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.
American Rock Salt Mine and surface facility looking east across Interstate 390. Note the shafts to the left and the stockpiled salt to the right.
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.
A solitary “sailing stone” on the Raceway Playa in Death Valley. (from Google Wikipedia)
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.
1947 photograph highlighting cavernous regions in the dam’s base that were filled with cement.