Description: If making more than one purchase, please read the note following the red text below! Manganese oxide dendrites on a platy basalt - hand/display specimen Dendrites are black films of manganese oxides that commonly grow on rock surfaces, on bedding planes and in cracks in rock. They are commonly, but incorrectly, believed to be the mineral pyrolusite. They are typically formed of the manganese oxide romanechite or of a hollandite-group manganese oxide, but not of pyrolusite, despite what you read in textbooks. Dendrites typically appear as branching structures that are misidentified as fossils of ferns. These unusual dendrites formed on the surfaces of a platy basalt. Water, rich in manganese and trapped at the rock surface, normally allows the manganese oxide film to extend and branch into a fractal-like distribution. Since the area where these were collected is arid, many did not progress far into the branching pseudofossil structure, but instead formed spots with incipient branches around each nucleation center, making the surface of the basalt plates occasionally look like the spots on a firehouse dog. Good as unusual examples that offer the opportunity for discussion of how dendrites form. The Tertiary basalt that hosts these dendrites is part of a dissected volcanic rim, the Doherty Rim, that rises above Guano Valley in Lake County and forms the edge of a plateau that stretches eastward through southeast Oregon just north of the Nevada line. Select a specimen: When more than one specimen is shown, you can select a particular specimen by telling us what is in the photo with it - a black mechanical pencil, a silver and black pen, or one of those plus some number of coins, or you can let us make the selection. Making multiple purchases? Just add items to your cart. When finished shopping, click on "view cart" and then click on “request combined shipping” at upper right in the Shopping Cart window. Do not proceed to checkout. We will send an eBay invoice with the correct combined shipping. Shipping: Priority Mail or Ground Advantage, whichever is cheaper. Rates vary by weight and zip code. We can ship for less than eBay will charge, and will refund the overpayment as soon as the box is packed. International customers: We sell and ship internationally. If eBay’s page does not let you enter your country name to determine the shipping cost for something you are interested in, please contact us. We can tell you what the shipping would cost and how to make the purchase. You can then decide if you wish to complete the transaction. Use the Contact Seller link in the Seller Information box on the right side of this page. Pay securely with your debit or credit card through PayPal! You do not need a Pay Pal account to do this. Yes, we do combine shipping!
Price: 10.45 USD
Location: Olancha, California
End Time: 2025-01-03T03:19:48.000Z
Shipping Cost: N/A USD
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Return shipping will be paid by: Seller
All returns accepted: Returns Accepted
Item must be returned within: 30 Days
Refund will be given as: Money Back
