Help identifying these

[Astrobouncer]

Here's some of the concentrate rocks from another spot I been looking at. Obviously the rocks on top sitting on the magnet are magnetite and some hematite. However the other shiny gray/black pieces on the bottom, I am not sure about. They are not magnetic. In the first picture you can see my thumb, to get an idea of the scale.

The bottom rocks most of them have high luster on one side, and the gray metallic luster on the other sides.

Is it pieces of lead? Or maybe silver? In the second picture you can see the high luster of a couple of the bottom pieces reflecting the lamp light. Thanks in advance for any help. I know the pictures are not the best but my camera has a problem focusing on small objects. Also this spot seems to have a lot of garnets and muscovite schist.

 

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[Astrobouncer]

Thanks Takoda. I didn't think about black pyrite.

This stuff came out of a creek that has a mountain spring feeding it. I will do a streak test later today using a ceramic tile and post the results. However I have a bunch of landscaping work to do soon as I finish breakfast

There is a good bit of these chunky heavy pieces there. I got all of the ones pictured (including the iron ores) from the material in one 5 gallon bucket.

Will keep you posted.

 

[Astrobouncer]

Did the streak test tonight and its leaving skid marks. The color is a light gray to gray. I crushed one piece with a quartz crystal and it seems to fracture easily. It comes apart like you are crushing a crouton. Damn, I wish I could find my microscope...

I might try burning some, and see if I can smell any sulfur.Any other ideas?

 

[Seamuss]

Work hard at processing all the stuff you can on site. Gold and pyrite associate in the same rock formation a lot.

Remember, if it sits at the bottom of the pan like gold, keep it. If it floats then it could be pyrite or gold flake with bad surface tention.

 

[Astrobouncer]

Here is a couple more pictures of a quartz vein I found only a couple feet from where I am getting all these heavies. You can see some crystals on that vein, as well as some of that same black metallic rock that is ending up in my concentrates. I also found a granite rock with lots of little garnets, that probably explains why there are so many garnets here. (Edit: added the small granite with garnets pictures). I added some arrows to the garnet pictures so you could see them easier.

 

[Goldwasher]

top pic iron oxide, bottom granite quarts intrusion? possable galena lead silver ore?

 

[BBad]

well, astrobouncer, you will keep me busy.

Just from the pictures I would tend to guess they are black tourmaline or hornblend which are extremely common (30 %+ or -) in most felsic (light colored minerals) igneous (derived from cooled molten lava) rocks. Another thought looking at the aggregated piece leads me to believe that those may be manganese nodules or iron-oxide nodules, especially when you say it 'crushed'. I am proud, you are using the right tools to determine the mineral type, but surely, go find that microscope as I have always hated ID'ing rocks on small samples. Save your eyes a bit.

Other things you can check are density or specific gravity which can be determined by weight/volume. Volume can be measured by the milliLiter (mL) in a very small graduated vial, or by guestimating its size (i.e., 1mm sphere).

Other ways involve taking thin section and using techniques for opaque minerals using a polarizing microscope. It may be possible to use some etching acids in different molar concentrations to get an idea.

These other ways are too involved which is why a geologist, if he cannot quickly ID the mineral, will just guess the most common and leave it at that, ESPECIALLY if you are looking for gold and need to keep the sluice going!!

 

[Astrobouncer]

Thanks, I think you are right about the it being manganese. I think it is probably this ore of manganese: http://www.galleries.com/Minerals/Oxides/PYROLUSI/PYROLUSI.htm

I am gonna get out there this weekend some and see if I can find some bigger pieces. The microscope I don't know, its packed away in the attic. I will probably wait till the temperature cools down some more before digging through all those boxes to find it. I don't think the minerals are going to go anywhere for awhile anyway, so no big hurry.

Thanks for the help!

 

[BBad]

I think you are on the right track with the pyrolusite, another thought I had was pyrhotite, which is a very slightly magnetic form of iron oxide.

If you get the microscope, look to see what crystal habit it is taking. It looks like crystal form so you want to look at the shap (number and orientation of faces) to put it in the correct crystal class. That would get you close. You can look closely at the broken portions to see how it cleaved (broke), that will tell you a bunch as well. Combine the results and that should narrow your search provided you have a good reference.

I would suggest Dana's book of mineralogy, THE ultimate mineralogy textbook, all geo students end up having one, mine is beat to hell.

 

[beaks]

just smash it and you will get the idea pretty fast.

 

[patches63]

that rusty red little glob on top of quartz reminds me of what i always find in creeks here. think its relic material cementing itself to host rock.rusty metal can turn into a goo after year in and out of the water,perhaps harden in a drought year?july dredging was throwing out huge chunks of resolidified rusty junk.if ther is pegmatite around your digs, check all heavies out.corrundums,beryl,garnet,tourmalines etc. think your right about those little rocks tho,some sort of ferrous mineral.

 

[beaks]

i have found plenty of gold in those globs of rusty trash because the cold will settle with the iron and cement in.

dont throw that stuff away, when in doubt "smash and pan"

 

[BBad]

i have found plenty of gold in those globs of rusty trash because the cold will settle with the iron and cement in.

dont throw that stuff away, when in doubt "smash and pan"

Very much agreed, something nice may be inside.