Monday, May 18, 2015

A Brief Geologic History of the U.S. (or how we learned to love rock hounding)

     My first introduction to rock hounding and polishing was through my grandfather in the early 60s.  He ran a small tumbler in his basement and introduced me to the wonders of Agates, Tiger's Eye, Opal, and Apache Tears.  I thought they were cool and kept a few for years.  About 10 years ago my best friend started to tumble a few of his own after several trips to Montana where he gave me several really beautiful Montana Moss Agates, probably still my favorite to this day.  To this day I still keep a small moss agate in my pocket as a good luck charm.  Little did I realize that Barb and I would so thoroughly enjoy this passion during our travels that we would actually plan trips around it.  Even before retirement we made several trips to the Upper Peninsula of Michigan in search of Lake Superior Agates, Jasper, Unakite, Fossils, Copper, and various lesser known varieties.  The UP is a treasure chest of the geologic history of North America.  The lakes themselves are evidence of the contoured path the great glaciers carved throughout their tour during the Ice Age. 

      I am still in the 'rookie' stage, having accumulated basic equipment, but a lack of area to display my treasures.  I do posses a dual 3 pound tumbler. well as a much larger 12 pound tumbler for larger loads of rocks. 
      Each batch of rocks from start to finish through the rough, fine, pre-polish, and final polish processes takes 8 weeks.  Of course any stones that you have jewelry aspirations for have to be shaped and drilled prior to polishing.  We are only beginning to experiment with this process this summer.   
      There is a virtual catalog of the different types of tumblers and polishing accessories, but suffice it to say that I have been very happy with my Thumler's Tumblers.  Their durable (and quiet) rubber barrels do a fine job with easy access to any spare parts needed.  Of course I now buy my polishing media in bulk sizes.  
      I was also fortunate enough to receive an older table model wet tile saw from my buddy that I equipped with a diamond blade good enough to cut small slabs or cabochons. 
      Although I would like a bigger, more professional rock saw/lapidary setup, the cost is far too prohibitive for my ambitions.  
      Retirement further broadened the opportunities to explore our passion.  Since April 2014 we spent the summer in Alaska and toured the U.S. from Michigan to Missouri, Oklahoma, Texas, New Mexico, Arizona, Nevada, California, Oregon, Washington, Idaho, Montana, and the Dakotas enroute back home.  Rockhounding for us has been leisurely exercise combined with relaxation and enjoying the great outdoors.  In addition, Barb has dabbled into the prospecting arena throughout our travels as well.  She panned for gold in Alaska, although she felt it was too much work for little reward.   
       She has had much more success panning for sapphires in Montana.  In two trips she has accumulated nearly 160 sapphires, including 9 gem quality stones that are being heated and faceted as I write this. 
      Interestingly, not all sapphires are naturally blue.  They have to be heat treated to obtain this color.  ONLY the Yogo Sapphires from near Utica, Montana are naturally cornflower blue.  These gems are fairly rare and expensive.  Even Princess Diana had one on her engagement ring; now Prince William's wife, Kate, wears it. 
      We also did a little prospecting along the shores of Ruby Resevoir in SW Montana this past trip.  Garnets are actually small slivers, sometimes pebble size, of Rubys.  Barb didn't find many of any size, but did accumulate nearly an ounce for her work. 


      We returned with probably 100 pounds of rocks from our recent winter trip.  This is but a brief sampling and history of some of them, both cut/polished and rough. 
 First of all, agates. 
      Most agates occur as nodules in volcanic rocks or ancient lavas, in former cavities produced by volatiles in the original molten mass, which were then filled, wholly or partially, by siliceous matter deposited in regular layers upon the walls. Agate has also been known to fill veins or cracks in volcanic or altered rock underlain by granitic intrusive masses. Such agates, when cut transversely, exhibit a succession of parallel lines, giving a banded appearance to the section. Such stones are known as banded agate, riband agate and striped agate.  In the formation of an ordinary agate, it is probable that waters containing silica in solution—derived, perhaps, from the decomposition of some of the silicates in the lava itself—percolated through the rock and deposited a siliceous coating on the interior of the vesicles. Variations in the character of the solution or in the conditions of deposition may cause a corresponding variation in the successive layers, so that bands of chalcedony often alternate with layers of crystalline quartz.
       Agates collected in Alaska come from various locations.  We explored the regions of the western edge of the Kenai Peninsula where agates are fairly common and come as a result of the frequent eruptions of Mount Redoubt, far to the west.  Salamatof, Nikiski, and Discovery beaches.   There is no real banding in Alaskan Agates due to the fact that the volcanic material, once blasted from Mount Redoubt and other volcanoes cools nearly instantly when landing in Cook Inlet, the Yukon River, or the Gulf of Alaska. 
      Montana Moss Agate…..Montana moss agate is found in the alluvial gravels of the Yellowstone River and its tributaries between Sidney and Billings, Montana. It was originally formed in the Yellowstone National Park area of Wyoming as a result of volcanic activity. In Montana moss agate the red color is the result of iron oxide and the black color is the result of manganese oxide.  Although it looks very much like embedded moss, these are actually dendrites, which in the best samples look very much like little trees or plants.  
      Crazy Lace Agate is a variety of banded Chalcedony, a mineral of the Quartz family. It is predominantly white, with layers of creamy browns, blacks and grays. Some may include layers of yellow ochre, gold, scarlet and red. FOUND SOUTHWESTERN NM
Petrified Wood: 
Found in many places......nuff said! 

       Malachite is a copper carbonate hydroxide mineral This opaque, green banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fractures and spaces, deep underground, where the water table and hydrothermal fluids provide the means for chemical precipitation.  Much like rust is to iron, malachite is to copper.

      Jasper is another of the harder minerals that takes many different colors depending on where you find it.  Usually red or brown in the UP, sometimes brown and banded in Texas.  Amazingly, even though Jasper is nearly as hard as agate, it sometimes takes on a delicate appearance.  Picture Jasper is just a jasper, but of such quality that it seems to represent scenery and when polished very nearly a desert picture.   

Rough geodes
Sliced Crystal Blue geodes
Large Baker Ranch Crystal geode 

Little Blue geodes
      Geodes are nodules erupted from volcanoes distribute the molten rock, quartz, and silica laden balls miles from the source……sometimes called Thunder Eggs, Dinosaur Eggs, or even Raptor Eggs.  The surprise is what’s inside, from agates to crystal to nearly anything. 

      These are my favorite.  Baker Ranch Geodes which originate from the Baker Ranch, 35 miles SW of Deming, NM.  These geodes exhibit redish brown agate material found rarely outside this area.  It is one of the few areas that exhibit agate centers with rich colors. 
      These are not even all of the rocks we brought back from our latest trip.  Many are still waiting to be cut and polished and some are already in the tumblers.  We get done with our normal summer chores around here in the next couple of weeks we're going to head out again in the RV to the Upper Peninsula in search of..........





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