monna0000
starting to spend too much on rocks
Member since May 2016
Posts: 243
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Post by monna0000 on Jul 16, 2016 8:37:14 GMT -5
What is the geological reason for most of the Stones here in the States have a kind of a Crust/different on the outside than the inside?
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causticyarn
off to a rocking start
Member since July 2016
Posts: 4
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Post by causticyarn on Jul 16, 2016 9:17:59 GMT -5
There are actually several different reasons. Minerals filling in cavities of volcanic rock, layers of minerals seeping in through crevices, mineral replacement. If you do a bit of studying on the subject, it can be quite fascinating.
(There are many more reasons, obviously, these are just the ones that make the rocks I am interested in)
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Jul 16, 2016 10:00:21 GMT -5
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ziggy
spending too much on rocks
Member since June 2016
Posts: 483
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Post by ziggy on Jul 17, 2016 16:26:24 GMT -5
What is the geological reason for most of the Stones here in the States have a kind of a Crust/different on the outside than the inside? I know its not the same thing as what you are asking in your question but, sometimes when I'm picking up rocks along the back roads I find ones that seem to have grown a, for lack of a better word, "skin" of what looks like a translucent layer of some sort of silicate mineral with embedded pieces of sand and gravel sticking to it where it was in contact with the ground. Close up showing the "skin" I was referring to. This "skin" only forms on the side in contact with the earth and is only superficial with no penetration into the rock itself. I find them a lot. At first I thought it might be a build up of road salt on the rock but upon closer examination it is way harder than salt. They look like agates at first until you see the whole rock. So, the point I guess I'm making is that the geological processes can be something as simple as laying in one spot for long enough with the atoms of the rock slowly interacting with the atoms in the surrounding soil it's sitting on or in, or the interaction with oxygen in the atmosphere, or being bombarded with UV rays from the sun, or minerals in the soil or water, etc.
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Post by fernwood on Jul 17, 2016 18:59:49 GMT -5
I have spent hours studying where I live. Skins on rocks can be caused by many different things, depending on the geographical location. In the states, rapid heating and cooling contributes a lot. Also the movement of rocks to the Eaerth's surface. Geology is extremely interesting and can help one select rock hunting locations. It can also help with ID's of finds.
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monna0000
starting to spend too much on rocks
Member since May 2016
Posts: 243
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Post by monna0000 on Jul 18, 2016 11:08:41 GMT -5
Sorry for absence, been driving through Texas and hit NM last Night. Thanks for all of the answers, it made me a bit wiser. In Denmark we only collect rocks at the Beach and what you se is what you get, so it has been a bit surprising to find that the rocks here look so different. I'll keep studing, it is quite facinating. We are in Deming and Will be hitting Pony Hills and rock hound State park + 1 or 2 rock shops today ;0)))
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