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Author Topic: Identify this rock/mineral?  (Read 66180 times)

Offline JimBob

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Identify this rock/mineral?
« Reply #25 on: 18/10/2007 01:53:20 »
No quarries nearby- the grooves are definitely some sort of layer in the rock, not drill holes.

Then I suggests the theory you proposed is most likely correct. It looks highly folded piece of metamorphic rock. That is, if the stuff that holds it together is the material that didn't weather  away.

Can rosey get a quart of milk, please?
 
 

Offline Karen W.

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« Reply #26 on: 18/10/2007 03:26:57 »
It looks like my pink quartz!!
 

Offline Bass

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« Reply #27 on: 18/10/2007 04:24:41 »
Pink quartz it is- also known as rose quartz.  Karen gets a notch on her rock hammer!  (this was way too easy for JB).
Next question, why is rose quartz pink?
 

Offline frethack

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« Reply #28 on: 18/10/2007 12:48:50 »
Iron and titanium inclusions (rutile needles) if I remember correctly.
 

Offline Bass

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« Reply #29 on: 18/10/2007 23:04:47 »
You nailed it, fretback.  Iron and titanium, often mixed with manganese, in the SiO2 matrix gives rose quartz its pink color.

Here's another.  Identify both the brown and green minerals (brown form well defined crystals, slightly harder than quartz).  Also ideas on how they formed.



« Last Edit: 19/10/2007 18:47:40 by Bass »
 

Offline JimBob

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« Reply #30 on: 18/10/2007 23:53:34 »
Are those barnacles or rugosa (or any type of) coral on the back in the shadows of the bottom picture?
 
 

Offline Bass

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« Reply #31 on: 19/10/2007 00:40:48 »
no, they're crystals.  Here's a close-up of the rock.
« Last Edit: 19/10/2007 01:04:42 by Bass »
 

Offline JimBob

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« Reply #32 on: 20/10/2007 04:29:17 »
The garnets I go, OK. The green mineral looks like malachite - which means water, hot or otherwise.

But genesis - that didn't dawn on me until I realized how well defined they garnet crystals are. They have been etched out of their matrix. Then the malachite makes more sense and the substrate is metamorphic. The water did all the work.

 

Offline Bass

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« Reply #33 on: 20/10/2007 19:09:00 »
Garnet is correct for the reddish-brown mineral.  The green mineral contains copper, but is not malachite (even though the original rock was carbonate).
What do you mean by "metamorphic"?  Hot water, as you point out, is critical.
 

Offline JimBob

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« Reply #34 on: 23/10/2007 03:38:49 »
I am still thinking about it.

HUMMMMMMMMMMMMMM >>>
 

Offline frethack

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« Reply #35 on: 23/10/2007 08:20:01 »
How about Chrysocolla or a very pale Azurite for the green mineral.  As far as genesis, the contact metamorphism of a carbonate rock might explain the garnets, substrate, hot water, and the copper needed for the green mineral.
 

Offline Bass

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« Reply #36 on: 23/10/2007 17:49:48 »
Contact metamorphic (or skarn) it is!  Frethack is referring to specific type of metamorphism where a hot intrusive (like molten granite) comes into contact with cold sedimentary rocks.  The heat and hot waters from the granite change the rocks surrounding and in contact with the granite.  Carbonate rocks (like limestone) are particularly prone to be changed because they are chemically receptive- the hot fluids break down the carbonate, releasing CO2 and allow the replacement by other minerals- in this case garnet.
Skarns form some of the earth's great ore deposits, and can contain copper, bismuth, molybdenum, gold, silver and a host of other minerals.  Most of the worlds tungsten supply comes from skarns.
This specimen is from a copper skarn from southern Nevada that was partially mined during World War 2.  While investigating this deposit for copper, we checked the surrounding area for tungsten and found a very large, buried tungsten skarn less than 300 meters away.  The company I worked for drilled over 100 holes and was ready to start mining for tungsten when the price dropped dramatically in the early 1980's- the deposit hasn't been touched since.
The green mineral is brochantite- a copper sulfate which is very similar to malachite (copper carbonate).
Kudos to frethack!
 

Offline Bass

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« Reply #37 on: 12/11/2007 05:18:48 »
soft metallic mineral mainly used in alloys.



 

Offline Karen W.

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« Reply #38 on: 12/11/2007 08:36:31 »
It looks like it has some kind of quartz in it.. maybe.. Looks kind of familiar.. something I might find around about here! some similarities!
 

Offline Bass

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« Reply #39 on: 12/11/2007 18:43:40 »
Hurrah for Karen, it does have quartz in it.  Metallic mineral will leave a stain on your fingers.
 

Offline Bored chemist

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« Reply #40 on: 12/11/2007 19:26:07 »
Is it noticeably dense?
 

Offline frethack

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« Reply #41 on: 12/11/2007 20:29:59 »
How about graphite
 

Offline Alandriel

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« Reply #42 on: 12/11/2007 20:39:24 »

I'm guessing..... Glaucophane ?
 

Offline Bass

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« Reply #43 on: 12/11/2007 23:11:38 »
Is it noticeably dense?
Close to, but a bit more dense than hematite (iron oxide) Fe2O3
 

Offline Bass

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« Reply #44 on: 12/11/2007 23:12:40 »
How about graphite
No, but graphite is soft and will leave a mark on your finger if rubbed.
 

Offline Bass

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« Reply #45 on: 12/11/2007 23:17:41 »

I'm guessing..... Glaucophane ?

Glaucophane (Sodium, magnesium, aluminum silicate), a mineral common in blue schists (word of the day) has the same fibrous appearance, but is too hard and not metallic.
 

Offline Alandriel

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« Reply #46 on: 13/11/2007 15:03:09 »

Apatite - that's the only other blue, metallic mineral I can find in my clever book

(second time lucky guess perhaps?)
 

Offline Bass

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« Reply #47 on: 13/11/2007 16:19:31 »
You might question your clever book then, Apatite (calcium phosphate) is non-metallic (I've never seen apatite that appears metallic). 
 

Offline frethack

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« Reply #48 on: 13/11/2007 16:50:16 »
Alright...another stab at it.

Tennantite

My little clever book says that its occasionally a raw material for arsenic

MmmmmMMmmMMMMMmMMmmmm...sounds like breakfast!
 

Offline Bass

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« Reply #49 on: 13/11/2007 17:34:26 »
Good thought, Molly would be proud of you.  Tennantite is a copper-iron-arsenic sulfide, a bit too hard and leaves a reddish streak (due to the iron).  This mineral is very soft and has a blue-gray streak.
 

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Identify this rock/mineral?
« Reply #49 on: 13/11/2007 17:34:26 »

 

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