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IdahoJim

Need Some Mineral Id Help

6 posts in this topic

I found an interesting rock while driving some back roads in northern Nevada a couple of weeks ago. It was lying next to the two-track, and I noticed it because it had a greenish tint. The country rock there is either rhyolite, or basalt, and dark in color. This rock is definitely an anomaly. It may be a lamproite tuff, or maybe it's simply a form of rhyolite. It is scratchable with a knife blade, but not easily. A couple of drops of muriatic acid had little noticable effect. The main rock was about 10" across. The piece in the pics is about 3" x 3" x 5". If anybody can help, I'd be grateful.

Jim

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A good reference for the "acid test" is:

 

http://www.geology.com/minerals/acid-test.shtml

 

The problem with guessing is that guessing is never conclusive. You may or may not believe one guess is better than another.

 

So, if it's important, get an assay. You have to specify the metal or other constituent you want to measure. It costs money to do an assay. :)

 

Next, one rock from the roadside, having no known source seems sort of irrelevant. It might contain diamonds if you crush it. The source of the diamonds remains unknown. The origin of the rock would have some bearing on what conditions and associative complexity of other related host rock that would unwind and provide clues to "what it is". It might be a rock sample thrown out by a geologist from Montana that needed room for more rocks!

 

No doubt, it's an interesting rock. Getting a full blown evaluation of "what it is" will require a professional hands-on view by someone skilled in mineralogy along with the willingness to take a little time out to really inspect the piece. 

 

Local universities that have a geology and geoscience curriculum will sometimes welcome visitors with a unique rock. The evaluation can be worthwhile even if they hand it back and tell you it is just common weathered granite.

 

- Geowizard

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Thanks,guys. I think my first approach is to crush the large remainder piece....the one in the pics I'm going to save. I'd like to see if there are garnets, or chrome diopside. I'm interested in gems, not metals. Then, I'm going to spend a few days down there looking at anthills, and checking the drywashes in the area....just a general prospect. I'd like to locate the source. I doubt the rock was thrown-out, but may have been hauled in from a gravel pit, though that material is usually crushed, and screened to a much smaller size. The area is along the western edge of the craton that underlies Wyoming, and northern Colorado, so it's a possible spot for a lamproite, or kimberlite. But, it;'s a big lavafield, too, so it could just be rhyolite tuff, though it stood out like a cherry in jar of mayonaise.

Jim

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IdahoJim,

 

Good ideas!

 

I have been researching the Mir diamond mine in Siberia. The mine has been closed for the past 7  years or so.

 

Spectacular diamonds. The best color and clarity I have seen! :)

 

The largest was 342.5 Carats.

 

Check it out when you get a chance.

 

So, Kimberlite pipes come to the forefront. I have been looking intensely at the geophysical mapping being done by the state of Alaska - looking for Kimberlite pipes.

 

In a couple of hours, 11:30 AM ADT, DGGS is publishing the results of a new survey! The East Styx survey. Kimberlite pipes are easily identified on these maps.

 

Do a search on the Chidliak project www.pdiam.com in North East Canada for a reference.

 

- Geowizard

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