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Phil Winkler wrote:From a Mo web site:
Geologists are unsure exactly how the chert formed in the limestone. Two possibilities are that oceans deposited silica along with the calcium carbonate shells of marine life, and the chert formed into sedimentary rock along with limestone. Another theory holds that chert formed later, when silica-rich ground water permeated spaces in the limestone. Whatever its origin, chert exists in limestone, and chert nodules, veins and layers are easy to see in road cuts through chert-bearing carbonate rocks.
graveleye wrote:John, the whole place is littered with small caves and rock-shelters. Not as many as there are when you really get into the far NW reaches of Georgia, but enough. When my dad had his well drilled they hit several voids, not that means much. They still had to go 300' before they hit water. But my brother says there is a shelter with a "crack" in the back that seems to go - breathes a little too. HA! So we set off down the hill and after about 20 feet I realized I am covered with ticks. Dads yard is the white-tail superhighway. You know how much I hate stinging sucking insects. I'm gonna wait now until after a hard freeze. That cave isnt going anywhere He says its not big enough to fit through, so if it looks like it goes, I am gonna need a digger.
Hatch wrote:What's a good model rock polisher to look for? I've always wanted one and now that I'm all grown up at age 38 I think I want to get one.
P.S. Just kidding...I'm not really grown up. Just ask my wife. Heh.
bigalpha wrote:yes! shiney rocks! I'm in.
Teresa -- while you cannot definitively say that the coloring of a rock is from one element/cation -- can you say that it's most likely from a certain element/cation? Or maybe, from a higher concentration of element/cation than other impurities?
I've ever seen purple or green granite
iron ore is gray and speckly (specular)
Teresa wrote: Can't say I've ever seen purple or green granite--though they may exist.
Colors can fool you though. Being a mean TA, I would give kids green fluorite and basalt with big pink phenocrysts for their tests. Not enough of those zingers to fail a student, of course, but one or two to humble the know-it-alls..
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