identifying rocks

[killswitchengage]

Hi

I would like your assistance to identify the rock formation in the following image

this rock has low but sustained reaction with HCl and the green minerals are easily scratched with the fingernails while the rest is not but can be scratched with a knife

 

[oldestguy]

I'd guess it is some type of metamorphic rock.

 

[dik]

Do you have a university with a geology department handy? or a lab that can do thin sections for viewing under a petrographic microscope?

Dik

 

[EireChch]

It looks like quartzite, but i aint no geologist.

 

[killswitchengage]

No its not metamorphic its volcanic at best , and yes i could search for a geologist but i cannot for the time being that's why i asked . Finally its not quartzite

 

[Ron]

Looks like a schist. Most schists are pretty hard but there are some softer ones. Where, in the world, is the origin? Schists are metamorphic but can be formed from igneous constituents.

 

[emmgjld]

Looks like a Breccia, volcanic. The broken core end views are good, but the core cut sides (out of focus) shown in the last photo look very similar to several volcanic deposits in Western Colorado. If a Breccia, It is probably very sensitive to normal geologic weathering, probably very poor concrete & asphalt aggregate, and will probably exhibit low resistance to abrasion/not so good as a gravel road surface. It will probably weather into clays, some with very nasty attitudes.

 

[dik]

My experience with schists is that they have a shinier and more platelike structure.

Dik

 

[Mad Mike]

Yeah, I started off my career as a decent geologist and not too much can be said from the photos- it's definitely volcanic, probably an agglomerate of sorts- if the green mineral scratches easily with your nail, it is almost certainly talc which appears to be contained in amygdales (originally gas bubbles in the hot volcanic extrusion). If the matrix scratches with a knife, it may be phosphate-rich...there are obviously carbonate minerals in there if it reacts with acid.

Pull out your regional geological map and descriptions and start there- at least a dozen different rock types could be linked to those photos- it's nice for a quiz thread but can't progress without a lot more details.

Cheers,
Mike

 

[fattdad]

longitude and latitude would help. Reaction to HCl is some tell.

Then again, it's hard to identify rocks in hand specimen without some context.

In light of what I know, I'll go on a limb and call this rock, "Leaverite." Leave 'er right there!

f-d

ípapß gordo ainÆt no madre flaca!

 

[fattdad]

p.s., carbonatite comes to mind. . .

https://en.wikipedia.org/wiki/Carbonatite

f-d

ípapß gordo ainÆt no madre flaca!