What Is In This Rock ?

[matthew textor]

Hi this is Matt

can anyone tell me what these crystals are on this rock

the crystals are shiny and are copper like color

I found it in a creek in Kennedy N.Y.

here is 2 photos

[Northern Sharks]

I'll hazard a guess and say pyrite

[2ynpigo]

It's often hard to identify minerals from photographs. Any way to get a pic at higher magnification?

The crystals look translucent and smoky in color, perhaps quartz. But I can't see them well enough to be sure of an ID.

[tracer]

i think i might be seeing some rhombic crystal shapes in the upper right, and the color could easily work with calcite, but what i don't know about this could fill volumes. nice mineral specimen, though.

[2ynpigo]

So three common minerals have been suggested.

I really doubt its pyrite as the grains are translucent and not opague. To be sure, if you can separate a grain, and crush it to a powder. Pyrite crushed to a powder is black (pyrite has a black streak). Crushed calcite and quartz are white.

If you can separate a grain, then put a drop of muratic acid, hydrochloric acid, or vinegar on it to see if it bubbles. Calcite, being a carbonate, will bubble in such acids. Note that the reaction to vinegar will not be as vigorous as to the other acids.

Alternatively, if the grain is calcite, it will not scratch glass. Make sure the glass is actually scratched and isn't just a powder of the grain left on the glass.

[MOROPUS]

Micaceous mineral?

[Frank Menser]

Next to impossible to ID something like this off a picture. There are too many things that can look like that. First we need a locality, State...County. Second, is the white rock quartz or calcite. Take a knife and see if you can scratch it. if you can it is Calcite if not - Quartz. This will narrow down the associated minerals a bit. I see no sign of clevages so i think we can rule out a white feldspar.

Once those things are established we can more accurately speculate on what those amber xls are.

[Shamalama]

Looks like a Mica in an eroded white Calcite matrix. Is it from New York or Ontario? if so then it's part of the Grenville group of metamorphic rocks. I've seen Phlogopite Mica in material similar to your picture from those areas. Again these are all big IF's, we really do need more location info.

Dave

[Auspex]

... we really do need more location info.

Dave

Mostly Matt hunts 28 Mi. Creek in Kennedy, NY. (Though that doesn't mean this piece came from there).

[Shamalama]

Mostly Matt hunts 28 Mi. Creek in Kennedy, NY. (Though that doesn't mean this piece came from there).

When I put Kennedy, NY into google, it takes me to fried chicken restaurants in NYC. Odd.

ok... found it... very possible to find that kind of rock near 28mi creek. Could be a glacial erratic transported down from Canada. I had a friend who specifically went looking for that material to find "gem" quality Phlogopite and blue Apatites. Forms very deep within the crust and it's part of a whole complex of metamorphic rocks called the Grenville Provence that was formed waaaaaay back during the Grenville Orogeny when the micro-continent of Avalonia mashed into Laurentia (future North America). Essentially it's a very coarsely crystalline Marble.

Dave

[Guest solius symbiosus]

I don't see anything there that looks metamorphosed. Too me, it looks felsic. Very weathered K-feldspar, plagioclase, a little micaceous stuff, and quartz. Probably a very weathered erratic..., but I'm not a hard rock guy.

[MOROPUS]

I don't see anything there that looks metamorphosed. Too me, it looks felsic. Very weathered K-feldspar, plagioclase, a little micaceous stuff, and quartz. Probably a very weathered erratic..., but I'm not a hard rock guy.

You look as if you were, though!

[Shamalama]

I don't see anything there that looks metamorphosed. Too me, it looks felsic. Very weathered K-feldspar, plagioclase, a little micaceous stuff, and quartz. Probably a very weathered erratic..., but I'm not a hard rock guy.

A acid test in Vinegar would answer the basic question of silicate or carbonate. If it fizzes or bubbles when submerged then it's a carbonate. If it were a plagioclase I would expect a different fracture pattern and maybe some cleavage but the relative smoothness of the white areas and slight translucency just reminds me of a calcite.

[Guest solius symbiosus]

Both calcite, and felspars, cleave easily; though one is orthogonal, and the other is rhombic. Too, for it to have that much calcite would indicate a carbonatite, and I don't think there are any of those in this part of the world???

But, like I mentioned, I am not a hard rock guy(are carbonatites even considered "hard rock"???).

[Shamalama]

I agree with you that both cleave easily but if the rock had been feldspar, I think the Mica would have less relief over the rock. To me it looks like the Mica has some books that are weathered and worn but others look somewhat intact. Mica is a much softer mineral than Feldspar and would scrape off sooner than the Feldspar in a Glacial or stream environment. But if the rock were carbonate then the Mica would remain longer than the more easily dissolved Calcite.

There are large marble formations in upstate New York/Canada that this rock could have come from. Another part of the Grenville Province rocks yield a china blue massive Calcite with flaky crystals of Graphite scattered within.

Sure Carbonates are "Hard Rock". Have you ever tried to crack the Laurel Dolomite to get a nice Gravicalymene?

[tracer]

i'm not seeing what ya'll are seeing. i've hung around a bit in the central mineral area of texas where there's eighty'leven varieties of granite and schist and micas and feldspars out the nostrils, and what i'm seeing looks like yellowish translucent crystals a la calcite or something with limey whitish junk all over it. (p.s. - i hate that i can't talk technical enough).

maybe i shouldn't be looking at this on a laptop screen.

matt - smash that sucker with a big hammer, and go out and buy a canon SLR and take a macro picture of the internal structure and post it.

wait, that might be too intense a methodology for the situation...

[jpbowden]

The brown crystals seem to be Bytownite, on maybe milk quartz can't tell the hardness from a picture. You can pick up a lot of these in Western New Mexico.

Bytownite

[mstreman]

I believe there is a 99% probability this is phlogopite in marble (aka Calcite) and possibly fluorescent. So, yes it is metamorphic. This is consistent with both local marble exposures both North East and East of where collected and/or material brought in by glaciers from Ontario. However, the fact that it has a pristine surface and is not coated in aragonite suggests it was recent and not where it was found owing to glacial transport. Given this was found in a creek and outside the marble belts , there is a chance this washed off a railroad right of way.

The material looks like material from

Balmat NY talc works--most always flourescent from this location

Limecrest Quarry near Franklin , NJ which is from the Franklin Marble Belt. Included the Farber Quarry, in Franklin and the Hamburg exposures.

Philogopite usually occurs in igneous rocks but it is also the most common mica in marbles. Philogopite from the Balmat region is yellowish to gold to golden brown and frequently glows yellow under SW UV.

Testing the rock with 10% dillute HCl ( 1 part muriatic acid with 2 parts water is close enough)will prove if it is calcite and positive flourescence with a UV SW lamp can strongly indicate it is is in fact philogopite.

Eman