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Offline Bass

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Identify this rock/mineral?
« on: 13/10/2007 04:04:09 »
I'm starting this thread with a hard mineral to identify-
any guesees (green mineral)?




Feel free to ask questions
Collected this in the Laramie Range, Wyoming.
« Last Edit: 13/10/2007 04:06:02 by Bass »


 

Offline jysk

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« Reply #1 on: 13/10/2007 05:33:07 »
Hi Bass,

Sort of a layered and somewhat metamorphosed sample. Nickel can stain green when oxidized.

Is this from a familiar deposit model?

Mike
 

Offline Bass

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« Reply #2 on: 13/10/2007 06:29:31 »
Highly metamorphosed, and layered.  Outcrop was about 60 meters long and 30-50 cm wide- the green color stuck out like a sore thumb.  No nickel.  Though rare, this mineral is mined in some areas- but I have never seen a deposit model for it.
 

Offline Karen W.

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« Reply #3 on: 13/10/2007 07:03:14 »
Is it copper or maybe THE MINERAL CUPRITE???
« Last Edit: 13/10/2007 07:14:23 by Karen W. »
 

Offline Bass

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« Reply #4 on: 13/10/2007 16:36:32 »
Many copper minerals are green, but this has no copper in it.  Cuprite is typically red.
 

Offline Bored chemist

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« Reply #5 on: 13/10/2007 17:10:11 »
Well, no Ni, No Cu, I'll try chromium.
 

Offline Bass

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« Reply #6 on: 13/10/2007 22:13:40 »
Now you're on the right track
 

Offline JimBob

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« Reply #7 on: 14/10/2007 04:03:37 »
My first thought was - Serpentine, gotta be a serpentine. So I started looking. I do not have the hardness, streak or any of those NORMAL things that are given on geology quizzes by the teachers who really care (flat earther indeed!) but I am a hardy old fart and kept pushing on deeper into the molded bush that is my geologic library. Couldn't find my Dana's - lost in a box somewhere in the outer reaches of the nevermore, but found first my Berry & Mason. Fairly helpful, that. Deer, Howie and Zusman (single volume, not 5 volume set) No help at all. One thing I did find though was that chromite is usually found with serpintines and ultra mafic metamorphic complexes. Mutters To Himself - dang thought I had forgotten all of this stuff because I have been a sedimentologist-subsurface stragtigrapher most of my carrier.)

So, This green schist (that was a geologic pun) is a former-pyroxene or amphibole rich in chrome ore serpintine just like the one mined in New South Wales, Australia.

From abstract - http://www.minsocam.org/ammin/AM53/AM53_162.pdf

"Altered chrome ores from the Coolac Serpentine Belt, New South wales, include chioritic
and nonchloritic assemblages. In the chloritic ores the primary chromite is usually an
aluminum-rich variety which is partly replaced by secondary chromite, or by a chemically
equivalent oxide mixture; and by chlorite. Chemical analyses of chromite concentrates and
electron probe scans across chromite variants show the secondary chromites to contain more
chromium, more total iron, more ferric but less ferrous iron, less aluminum and less magnesium
than the primary chromites. Much of the chlorite developed from serpentine and
pyroxene; when aluminum, released from chromite during oxidation, became avaiiable.
Some chlorite which originated in other ways, however, occurs in the same ores."

This of course, I did not find in a book on my shelf, but in a copy of the American Mineralogist on the web.

SO what we have here is Chromite, probably as (Mg,Fe)OCr203 - derived from pyroxenes and amphiboles and in a serpintine matrix. The green minerals can include chromite and the serpintine phylosilicates - chrysotile, a type of asbestos, antigorite and lizardite.

( This was refreshing - even if I am wrong - I have been thinking about manganese-rich cherts this whole week.)

Do I get a prize or am I just too old to understand? I would prefer boobies as the prize. And NO - NOT DEAD BIRDS, DUMB ARSE!
« Last Edit: 14/10/2007 04:27:13 by JimBob »
 

Offline Bass

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« Reply #8 on: 14/10/2007 04:27:06 »
Silver star, but not quite the gold star.  Really close, but there is no serpentine in this specimen.  Hardness= 2 to 3   Streak= colorless  Cleavage= perfect 1 direction Crystal system= monoclinic

We have a problem if it's my boobies you want as a prize.
« Last Edit: 14/10/2007 04:30:07 by Bass »
 

Offline JimBob

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« Reply #9 on: 14/10/2007 04:29:28 »
OK, I saw that in the article of the abstract - back in a sec.
 

Offline JimBob

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« Reply #10 on: 14/10/2007 05:49:40 »
Before my eyes close in slumber - and without really doing all of my homework I will offer up for examination the mineral Chlorite - monoclinic, 2-3 hardness colorless streak and a precursor of chromite before metasomaitc activity.

If I do win the boobie prize, it will be one of you stunningly sumptuous 18-year old FEMALE students who just loves older men. Whatever gave you the impression you were that hot? Huh? Huh? Huh?
 

Offline Bass

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« Reply #11 on: 14/10/2007 17:24:23 »
Chlorite- no.  Don't know that I've ever seen chlorite quite as bright green.

Me, hot? Definitely not! The only heat I generate these days is rubbing Ben-Gay on sore muscles.
 

Offline frethack

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« Reply #12 on: 14/10/2007 18:07:25 »
Glauconite?
 

Offline Bass

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« Reply #13 on: 14/10/2007 18:26:33 »
Good guess, but no.  It does contain chromium and JimBob was close on the mineral species when he postulated chlorite.
 

Offline JimBob

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« Reply #14 on: 14/10/2007 21:58:08 »
Covering all bases

Sheridinite, also known as Grochauite, a dark green clinochlore that is sometimes chrome-bearing. It is mined for chrome in Switzerland.

Chrome-Pyrophyllite and/or Vauquelinite is/are a green phylosilicate mineral that fits the bill as well.

pyrophyllite has a hardness less than you gave but I think the chrome in the crystal structure could harden it a little.

I have also seen talc this color and structure and talc is very closely related to pyrophyllite.

Vauquelinite is a green phylosilicate mineral that fits the bill as well

Mariposite is Green and a chrome mineral that fits the bill but ...... just don't seem right, Bubba

Knorringite is a green chrome mineral but is a tracer mineral for finding kimberlite pipes

Uvarovite is a green garnet group mineral high in chrome but hard as garnet

(Sheridinite is named for Sheridan County, Wy but isn't in the Laramide Range.)
I am going to watch Dallas and New England.
« Last Edit: 14/10/2007 22:21:58 by JimBob »
 

Offline Bass

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« Reply #15 on: 15/10/2007 00:02:05 »
The mineral is fuchsite (pronounced with long u), the emerald green variety of muscovite (mica).  Chromium in the crystal lattice gives it the distinctive green color.  In places, it is rich enough in Cr to be mined.  Also commonly found with embedded rubies.  Fuchsite is rare, but has been found in locals around the world.

JimBob was close enough with Mariposite to get credit for this one!  Way to go JB!

Next specimen will be more common mineral/rock.

 

Offline JimBob

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« Reply #16 on: 15/10/2007 02:26:41 »
NOT IF I GET ONE UP FIRST!


(When will your "Student Assistant" arrive?)











Color: yellow brown- brown - Habit: Commonly rhombohedral, also quite variable - Streak: white - Hardness: 3.5-4

common mineral, found in sediments, metamorphic terrains and in hydrothermal veins (The sting is for delicate handling.)


 

Offline Bass

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« Reply #17 on: 15/10/2007 17:32:04 »
You dog!!

Assistant will arrive on Tuesday- I assume you can pick her up at the bus station?  Potwani doesn't speak much English, but she works for cigarettes, which is why I keep her around...



I'm guessing your mineral is showing it's side rite well.  This is one of the indicator minerals in the Coeur d'Alene mining district, famous for it's huge lead-zinc-silver mines.  I've never seen it in such beautiful plates like that, though.  Where did you collect the specimen?
 

Offline JimBob

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« Reply #18 on: 15/10/2007 18:16:55 »
I bought the Siderite (FeCO3) at a rock shop. Never did get that lucky in the field - although I did find a 2 karat diamond at Herkimer, Arkansas during a drilling break in a well I was sitting - extended fishing job. Drill collars twisted off.  (Attemting to rest my eyes, I realized that there is no Herkimer AK. Herkiker "Diamonds" are doubly terminate quarts crystals. - DOH!)

Since the rock shop was in New Mexico, I think it was a secondary deposit in a sand dune. There are no detachment breaks where it came off of a larger piece or from a growth platform. There are also no sand grains included so that is a little strange.

Potwani - This could work. She can sleep in the shed and grind my corn. That is a really tiering job for an old man like me. But I believe I specified "sumptuous." Either you cannot tell the difference between "sumptuous" and "something" OR, more likely, desperation has driven you to this low level. I am really sorry about it, in either case. I extend my sympathies.

Now your turn:

Post something - I am going to run out of specimens quickly as I have most in storage.
« Last Edit: 16/10/2007 03:50:04 by JimBob »
 

Offline JimBob

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« Reply #19 on: 15/10/2007 18:30:32 »
The mineral is fuchsite (pronounced with long u), the emerald green variety of muscovite (mica).  Chromium in the crystal lattice gives it the distinctive green color.  In places, it is rich enough in Cr to be mined.  Also commonly found with embedded rubies.  Fuchsite is rare, but has been found in locals around the world.

JimBob was close enough with Mariposite to get credit for this one!  Way to go JB!

Next specimen will be more common mineral/rock.



Thanks for the credit - Since the Mariposite wasn't emerald green, and the only picture I could find was in a metamorphic carbonate I didn't feel comfortable with it. It is good of you to be so generous.
 

Offline Bass

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« Reply #20 on: 16/10/2007 02:17:16 »
A friend of mine was recently diving in Flathead Lake and found this interesting rock. 






This rock may have been in Flathead Lake for thousands of years.  It is obviously well-rounded, which means it had to be quite solid while it was tumbled about in streams/rivers before coming to rest in the lake.  The hard ribs are either siltite or argillite (metamorphosed silt or mud) and can barely be scratched with a knife.  The material in the cracks is very soft- can be scratched with a fingernail.

My best guess is that the material in the cracks contain carbonate (limestone), which could weather out chemically while underwater- possibly deposited as a limey mud back in Ye Olde Precambrian Days.  Have not tried acid to see if it effervesces yet.

Any other ideas?
« Last Edit: 16/10/2007 02:19:19 by Bass »
 

Offline JimBob

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« Reply #21 on: 16/10/2007 03:07:55 »
How close is the lake to a quarry?
« Last Edit: 16/10/2007 03:47:47 by JimBob »
 

Offline Bass

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« Reply #22 on: 16/10/2007 04:32:54 »
No quarries nearby- the grooves are definitely some sort of layer in the rock, not drill holes.
 

Offline Bass

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« Reply #23 on: 16/10/2007 04:54:44 »
As promised, here is a much more common mineral.  Hardness=7  Cleavage=none

Collected in pegmatites in the Black Hills.
(we've had a warm October, as you can tell by my green grass- still mowing in Montana, GRRRR!)




« Last Edit: 16/10/2007 04:56:40 by Bass »
 

Offline JimBob

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« Reply #24 on: 17/10/2007 00:43:28 »
Now that is a bit too easy.
 

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