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Two reference books I've found particularly helpful are: Sparky Stensaas' "Rock Picker's Guide to Lake Superior's North Shore" and Susan Robinson's "Is this an Agate." Armed with Sparky's and/or Susan's book plus some of the pictures and descriptions I've provided here, perhaps will help you ID what you are collecting. [Recently I've found another rock pickers reference book that is helping me with agate hunting. It's "Understanding and Finding Agates By the way, if you want to print out any of these larger images, just *right click* on the image and choose "copy image" to copy it to your hard drive. Once there you can click on it and print it out.
~~~"Click" on smaller images for a larger picture~~~ |
Quartz Quartz is a common mineral found among the beach stones, very hard (will scratch glass), somewhat translucent like frosted glass, and be white to yellow to grayish in color (impurities cause this variety in colors). Generally found as pebbles or imbedded in other rocks. In fact some of the pebbles were formerly amygdules that broke loose from the rock in which they were imbedded.
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Calcite Calcite (calcium carbonate) at first glance may be thought to be quartz as it is a similar color (white to yellowish) and also commonly found, both as pebbles and imbedded within other rocks. But scratch it and you'll see it is much softer than quartz - chalky. To the far right is an amalgam of quartz & calcite > > >
) ) Chert Cherts are a tiny crystal form of quartz. Impurities make them less translucent than quartz. They have a waxy appearance, somewhat shiny. Some of these depicted in the picture "may" be chert. The stone on the far left seems to best meet the description and may be Jasper.
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Flint Flint is a black version of chert. Note the waxy, somewhat shiny surface. ) |
Agate Here's an agate from the display at the Minnesota Geology Center in Moose Lake. Go here to see more examples of agates - both rough and polished.
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|  Is This a Lake Superior Agate? |
When I picked this guy off the beach at Black River Harbor, Michigan in 2008, I thought I had finally found my first Lake Superior Agate Beach Rock. But now I'm not sure? Agate Hunters and Rock Pickers - what do you think? Let me know your guess. --Ross - roscoe@superiortrails.com
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Many beach rock pickers might think this beach rock is an agate due to its banding and chochoidal fracture pattern. But I think this rock is a banded chert. The bands formed similar to how they form in a true agate but the crystal granules are so tight that the rock is opaque rather than translucent or partially translucent. Also the color is atypical of a Lake Superior Agate.
) ) The beach rocks below ARE Lake Superior Agates - no question about it! |
Jeff King of Pickford, Michigan sent me some pics of 3 agates he found during the summer of 2009 on Lake Superior beaches near Munising, MI - - - Great finds Jeff, I'm jealous.
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Want to See More Agates - Go Here for pix from the Lake Superior Agate Museum |
Links for Rock Picking on Lake Superior Beachs and information on Agates and Rocks found around Lake Superior
For a nice introduction to rock tumbling, see Cheralyn Maturi's Minnesota Iron Range Website |
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" by Karen Brzys. )
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Understanding & Finding Agates
