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kaitb
climber
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Jan 11, 2010 - 12:44am PT
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Minerals: Okay boys....I think I got a good educated guess as to what the "green" mineral is. I could be kinda cheating considering I got a few tips from being out in the desert this past week with Bryan looking at geology. But here it goes: Chrysocolla?
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kaitb
climber
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Jan 11, 2010 - 12:54am PT
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But the more I look at the image - the green mineral is brighter than the normal turquoise color for chrysocolla - so it just may be malachite. Chrysocolla is a hydrated copper silicate and malachite is a copper carbonate - so both are minerals associated with copper ore bodies.
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Jaybro
Social climber
Wolf City, Wyoming
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Jan 11, 2010 - 12:57am PT
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one of those slickensides, artifacts?
I've seen it in the field...
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Srbphoto
Trad climber
Kennewick wa
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Jan 11, 2010 - 12:58am PT
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Looks a lot like the ribboned chert at Glen Park in SF.
The rock at Battery Spencer is the first place I went when I bought my first climbing shoes (Fires) in 1982.
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Minerals
Social climber
The Deli
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Jan 11, 2010 - 01:02am PT
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Fritz, you are correct on all three. Nice work!
The galena has been exposed at the surface in a mine dump and has lost its Metallica luster but the cubic habit is still obvious, giving us the clue. There is also a bit of sphalerite in there as well – it’s a sulfide deposit.
Right on, Kait!
Yup, malachite filling fractures in either sandstone of the Jurassic Dunlap formation, or limestone of the Triassic Luning formation (according to the Mineral County geologic map)… I forget exactly. There is also a bit of blue chrysocolla in there as well.
The last two outcrops are located along the JMT, Sierra Nevada.
Galena:
http://en.wikipedia.org/wiki/Galena
Sphalerite:
http://en.wikipedia.org/wiki/Sphalerite
Malachite:
http://en.wikipedia.org/wiki/Malachite
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apogee
climber
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Jan 11, 2010 - 01:22am PT
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Can someone provide a layperson/geo-lurker explanation of the formation of epidote?
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Minerals
Social climber
The Deli
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Jan 13, 2010 - 04:51pm PT
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Basically, epidote forms under certain metamorphic conditions with the presence of hydrothermal fluids and chemical/temperature/pressure conditions that favor epidote instead of the higher-temperature primary minerals that the rock was originally composed of. Primary minerals (plagioclase feldspar, etc.) are chemically “hydrated” and altered to form epidote.
From Manual of Mineralogy, 20th ed., 1985:
“Epidote forms under conditions of regional metamorphism of the epidote-amphibolite facies. Characteristic associations of actinolite-albite-epidote-chlorite occur in the upper part of the greenschist facies. Epidote forms also during retrograde metamorphism and forms as a reaction product of plagioclase, pyroxene, and amphibole. Epidote is common in metamorphosed limestones with calcium-rich garnets, diopside, vesuvianite, and calcite. Epidotization is a low-temperature metasomatism and is found in veins and joint fillings in some granitic rocks.”
More info on epidote:
http://www.answers.com/topic/epidote
Hydrothermal alteration:
http://en.wikipedia.org/wiki/Hydrothermal
Metasomatism (a type of metamorphism):
http://en.wikipedia.org/wiki/Metasomatism
Skarn:
http://en.wikipedia.org/wiki/Skarn
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dipper
climber
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Topic Author's Reply - Jan 13, 2010 - 06:37pm PT
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A few more samples from my collection of ballast.
What I am told is epidote
Epidote other side
From inside the crater west of 395 at Deadman Summit
Crater sample 2
Little Colorado abalone pounder
Big Sur coast (rock's name is Lono, as in Curse of, H.S.T)
Are these agates? (From same location as image in first post of this thread
Great Western Divide (glacial polish all of side you see)
Matterhorn (Calif. version) (the long dark lightning bolt thingie)
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Minerals
Social climber
The Deli
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Jan 13, 2010 - 08:34pm PT
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Fritz’s garnet photos inspired me to try a few photos of some of my samples. I grabbed these two yesterday, because they were at the top of the monstrous mound of rock that is in my storage unit. These aren’t great photos, but they are the best that I could do with my current 4-megapixel hand-me-down camera. I’ll have to grab some more samples at some point. OK, a couple more mineral quizzes…
The orange-brown mineral is garnet (grossular or andradite). What is the white mineral?
This sample contains a bunch of garnet with nice, diamond-shaped crystal faces. The white minerals are quartz and calcite. What is the black mineral?
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Minerals
Social climber
The Deli
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Jan 13, 2010 - 09:01pm PT
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Nice samples, Dipper!
Yeah, looks like epidote on a fracture/fault surface in your first two photos. You can see slickensides (parallel lines) and maybe even a slight mineral lineation on the green surfaces. Looks like some pink K-feldspar… a chunk of granite?
Is the second “crater” sample all one piece? Looks cool, like it should be a proud pillar to support a personal treasure. Or maybe just a place to put a beer, provided you set it down properly…
Lono is a cool rock. Some sort of conglomerate?
Those pebbles look like agate or milky quartz.
Nice chunk of foliated granite/granodiorite with aplite dikes.
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Paco
climber
Montana
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Jan 13, 2010 - 09:21pm PT
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It looks to me like foliated metamorphic rock: The white band must be quartzite- but nobody ever called me a geologist.
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Fritz
Trad climber
Hagerman, ID
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Jan 13, 2010 - 10:14pm PT
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Dipper: I am so glad you have continued this thread!
Since I have a “rock hound” background, I will take the agate question. However, anything I say may be corrected by Minerals.
Agate falls into the Chalcedony family of silica minerals. http://en.wikipedia.org/wiki/Chalcedony
However, the “rock hound” definition is: Agate is translucent quartz with a milky texture, or is colored, or shows banding. A piece that is obviously quartz that doesn’t fit this definition is further divided into:
A. Milky Quartz (or the old-timer name: “bull quartz.”)
B. Jasper: has the shinny and hard quartz look, but is colored and opaque.
Another test for quartz is a fracture test. Quartz minerals always have a glass-type (conchoidal) fracture that leaves a very sharp edge with smooth shell-like curves.
Of course all rockhounds define agates still more.
Yah have “Keepers or Perfects.”
Then there are the “leaverites.” (Leave it right there).
And finally the sex stones:
“That’s just another forking rock!”
So-----to finally answer your agate question. I agree with Minerals: the two on the right are agates. The other two are probably water-polished milky quartz and are “leaverites”
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Fritz
Trad climber
Hagerman, ID
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Jan 13, 2010 - 10:25pm PT
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Minerals: Great of you to dig out and post up more garnets.
Re your question on the white crystals. Without looking at a book, I thought "is there such a thing as white Staurolite?"
However with a quick look at a book to check my #2 guess: I see that Kyanite does occur in white and Staurolite does not.
Kyanite is my guess and I'm sticking to it.
Re. the small grey metalic looking stuff. Gun to my head---I would be forced to guess some kind of copper mineral. I really don't have a clue.
I will return the difficult metalic mineral question to you soon!
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Minerals
Social climber
The Deli
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Jan 13, 2010 - 10:45pm PT
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Fritz, nice job with the quartz description! Sounds good to me. But I am still learning here too, and have to read to brush up on some of the details in order to post. Got a few textbooks here and will read up on garnets some more.
I wish the other guys would post up again. Too much surface geology? Hmmmm… BASE and Tradster, where are you guys? Probably busy with real things…
Re. My last mineral quiz. White mineral… The type of garnet is a hint…
And the second mineral is black, not metallic. This mineral is fairly common.
It’s tough to really see rock/mineral samples on a computer screen, compared to holding the sample in your hand.
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Fritz
Trad climber
Hagerman, ID
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Jan 14, 2010 - 04:16pm PT
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Minerals: My final try at IDing your white mineral crystals is: Wollastonite. Not much of that in Idaho. I had to cheat and research skarn minerals.
Here are some easy to ID specimens from a copper mine in an altered limestone skarn.
OK: Then we have the 3M (mystery metalic mineral) special I am not sure of. I have an old USGS report on this location. Only metalic minerals mentioned are iron minerals, molybdenite,and copper minerals.
This mineral cleaned up to a silvery metallic look as in the first photo. It formed thin layers in that green mineral in photo 1, and edge-on almost had a mica-book look to it. In the wild it was much darker as per the last photo.
I ended up putting a mild solution of chlorine bleach on one of the cleaned up specimens that grew mold, and it darkened almost to a black color.
I have a guess, but I really don’t know what it is.
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Fritz
Trad climber
Hagerman, ID
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Jan 14, 2010 - 05:40pm PT
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Weschrist: Yes I am. It started dark, and I cleaned the specimen in a vinegar solution, then soap and water: and the mineral got shinny.
I made the mistake of putting a couple that were not completely dry in a sealed container and they molded. When I killed the mold with a very dilute bleach solution: the shinny got dark again--maybe darker than when I found them.
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Fritz
Trad climber
Hagerman, ID
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Jan 14, 2010 - 07:29pm PT
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weschrist: Nope not Fritz from SLC. I can't help you with hardness and streak, other than "it ain't real soft and it ain't real hard".
I will agree the shinny photo looks like galena. It is not galena.
I am 99% sure it fits into one of the categories I cited: iron minerals, molybdenite, or copper minerals.
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Jan 15, 2010 - 02:48am PT
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Great stuff everyone. Just got back from Colorado, so here are some geo photos from the trip.
Barringer Meteorite Crater near Winslow, Arizona taken on the flight from Phoenix to Durango. One of the best preserved meteorite craters on the planet. Estimated to be 50,000 years old. It is 1,200 meters in diameter & 170 meters deep.
http://www.meteorcrater.com/
This photo also taken on this flight. Not sure what canyon this is but it has some cool desert towers. Anyone recognize it?
This photo was taken near Telluride. I believe these are Tertiary volcanic rocks of the San Juan Formation but I'm not sure.
This photo was taken from the Ames Hydroelectric Power Station outside Telluride where the famous Ames Ice Hose climb is located. Not sure what formation it is but thought the structure looks interesting.
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Minerals
Social climber
The Deli
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Jan 16, 2010 - 01:39pm PT
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Fritz, you are correct. The white mineral is wollastonite.
Wollastonite:
http://en.wikipedia.org/wiki/Wollastonite
More nice photos, Fritz.
The first looks like epidote, with a little bit of garnet.
The second looks like garnet and chrysocolla.
The third one looks like epidote, chlorite, calcite (shiny cleavage surface), and your metallic mystery mineral.
Does this look like your metallic mystery mineral?
Any guesses on the jet-black mineral yet? Here’s another photo of the mineral:
More epidote, with chlorite (darker green) on the left side of the photo; the white is quartz (May Lake area, Yosemite):
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Minerals
Social climber
The Deli
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Jan 16, 2010 - 01:46pm PT
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Tradster, you are back! Cool.
Nice photos! The one of Meteor Crater is neat – nice view and nice light! The sinuous drainage pattern in the background gives it a little bit of scale.
Neat colors/layering in the Tertiary volcanics.
Yeah, some neat structure in your last photo, and some interesting rock – maybe even to a climber!
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