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Identity HelpMineral hill finds

16th Mar 2018 14:12 UTCDominic Randazzo

Found these minerals on a recent trip to mineral hill in MD, any idea as to what they might be?

16th Mar 2018 14:13 UTCDominic Randazzo

16th Mar 2018 14:15 UTCDominic Randazzo

16th Mar 2018 14:16 UTCDominic Randazzo

16th Mar 2018 15:12 UTCDonald B Peck Expert

Dominic, What you have are rocks, not minerals. Rocks are comprised of minerals, usually more than one, but not always. Your rocks appear to be either a schist or gneiss. They grade into each other and are sometimes difficult to tell apart. A mineral in your rock appears to be chlorite. It is a green sheet mineral, like mica, and forms thin flakes, often in memtamorphic rocks. Schists usually break parallel to the foliation (leaf like structure resulting from the chlorite flakes lying parallel to each other). Gneisses break, usually, in blocks. The top photo is certainly a schist. So are nearly all the others. The 8th photo could be from a dike and could be quartz, or perhaps calcite. Drop some vinegar on it and watch for bubbles to form. If they do it is calcite, If not probably quartz, in which case you cannot scratch it with the tip of a knife.

Don

16th Mar 2018 15:24 UTCKeith A. Peregrine

The light green material is most likely Malachite. There is talc at Mineral Hill, so if you can scratch something with your fingernail and leave a mark, it is talc. As Don mentioned, chlorite is present. Actually, there is a lot at Mineral Hill and is a darker green than the Malachite. If I remember correctly, if something looks mineral green and has a shiny, flat or curved surface, it will be Chlorite.

If you have a magnet, run it over your rocks. Magnetite is present as small, roundish dark grains (poor word, but that's all I can think of at the moment). May be the size of BB's if you are familiar with them. If you see something like this, but it does not attract the magnet, then you've most likely found a variety of chromite.

If you are from the area, I would strongly suggest you visit a rock club and obtain their thoughts. Someone surely would be familiar with the kinds of rocks and minerals present at Mineral Hill.

Beautiful walk!

Keith

16th Mar 2018 15:47 UTCDominic Randazzo

-- moved topic --

16th Mar 2018 18:01 UTCAlan Pribula

Dominic:

Bring these to the next meeting of the Baltimore Mineral Society (check the website at baltimoremineralsociety.org for meeting times/dates and directions to the meeting site). A number of the members have collected at Mineral Hill and would be glad to give you some help ID'ing your finds.

17th Mar 2018 02:16 UTCDominic Randazzo

The very first photo looks like actinolite to me, because when you zoom in it appears to have the kind of feathering/curved crystal formation.

17th Mar 2018 02:16 UTCDominic Randazzo

And the last looks like coal in the other photos I looked at.

17th Mar 2018 11:15 UTCHarold Moritz 🌟 Expert

I think that area is one of several serpentinites around Baltimore, some where mined for chromium, and most of the rocks above look like they could have come from that or related Ca-Mg-rich metamorphic geology, except the piece of coal at the bottom, clearly brought in by humans for fuel. Chromite looks like magnetite (same mineral group). Cr weathering out of the rocks has limited the plant growth in these areas (as it does in serpentinites around the world). A little copper is usually also present, hence the green alteration, which stands out to the human eye and so is often picked up even when actually rare at a location. I see a chunk of marble in the pix, also common in the area.

17th Mar 2018 16:47 UTCStuart Herring

Hi Harold,

I hate to tell you that you are way off track with these specimens being utramafic-serpentine related. This area is 4 miles to the west of the nearest Serpentine Barren - Soldiers Delight. I do not doubt that they came from Mineral Hill Mine area though. I belong to the same club as Al Pribula, and would be more then happy to examine these specimen in person.

Yes the last pic does "look" like coal. That chunk of "marble" also looks like talc to me. Yes Dominic the first pic does "look" like actinolite.

Also marble is not common in either area of mining...quarried rock, usually Cockeysville marble used for irrigation/drive ways/road metal. The nearest marble deposit is in Marriottsville, many miles south of Mineral Hill Mine.

17th Mar 2018 18:03 UTCHarold Moritz 🌟 Expert

Well, I took a stab at it from memory of time spent down in the Baltimore area...but really, if anyone want rocks truly IDed they need thin sections. Some lo-res, full view photos of things with tiny grains doesnt give us much to work with.

17th Mar 2018 23:23 UTCDominic Randazzo

I don’t think the photos have that poor of a resolution, I think there pretty good considering there taken from an iPhoneX, but I can see why there they’re not as useful as a professional camera because zoomed in it gets kinda pixelated.

The suggestions and educated guess are very much appreciated and help with id’ing the specimens, and I would love to attend one of the Baltimore mineral society meetings but it just so happens they land on a Wednesday, which makes it impossible for me to attend. Thank you for taking the time to examin the pics and giving your best guess as to what they might be.

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