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Post by RocksInNJ on Nov 12, 2019 12:53:34 GMT -5
I found this 21lb monster in a stream running into the Wissahickon Creek in Pa. not far from the Valley Green Inn and have been wondering what is is. My best guess would be a Smoky/Rootbeer quartz, but am looking for clarification, as I don’t know much about rocks. There’s really not much for good rocks in my area and this has been my best find thus far. I’d also like to know if it would be able to be cut on a tile saw? I’m hoping to make some slabs and shapes for tumbling, if the tile saw I want ever goes on sale again. Any help would be highly appreciated.
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fuss
spending too much on rocks
Member since October 2018
Posts: 250
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Post by fuss on Nov 12, 2019 16:18:15 GMT -5
iron stained quartzite or massive milky quartz is my 2 cents. It is not smokey quartz though.
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Post by captbob on Nov 12, 2019 18:49:42 GMT -5
Put a couple drops of vinegar on it. If it bubbles, that may be calcite.
Tough to make a call from the pictures, but calcite is my guess.
Quartz is way harder than calcite. A scratch test may help also.
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Post by RocksInNJ on Nov 17, 2019 0:27:20 GMT -5
So I tried putting some vinegar on it and there were no bubbles, so I guess it’s not calcite. Quartzite would be great if thats what it is, cause I believe it should polish up nicely.
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Post by fernwood on Nov 17, 2019 6:31:14 GMT -5
If Quartzite, it should have the appearance of brown sugar. Very fine grained crystals.
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Post by RocksInNJ on Nov 17, 2019 13:32:33 GMT -5
If Quartzite, it should have the appearance of brown sugar. Very fine grained crystals. I’ll have to take another look and maybe include a close up picture. Would love to figure out what it is.
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NDK
Cave Dweller
Member since January 2009
Posts: 9,440
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Post by NDK on Nov 17, 2019 14:11:21 GMT -5
You may be surprised what color it is inside. Smash it up & tumble it, should polish nicely.
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NRG
fully equipped rock polisher
Member since February 2018
Posts: 1,630
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Post by NRG on Nov 22, 2019 15:47:38 GMT -5
Does known quartz scratch it? If so, then it could also be a feldspar.
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Post by greig on Nov 22, 2019 17:36:24 GMT -5
Do you have access to muriatic acid? That would be a better test than vinegar. Streak is a good indicator. Hardness would also be a good clue. You can scratch calcite (3 on Mohs) with a knife (5), but not feldspar (6+) or quartz (7). It is difficult to ID a rock by picture, especially one that has been in water. Even so, without other evidence, I would vote quartz for now.
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Post by RocksInNJ on Nov 22, 2019 21:08:40 GMT -5
I’m not familiar with scratch test and what to look for, but I did take a steel drill bit and scraped it back and forth over the rock several times. It didn’t leave a big white mark or any signs of scratching like it does on the softer rocks, but there was a very and I mean very minimal darker line, but when wiped with a dry finger there were no signs of any marks or scratches what so ever, so I don’t know if the slight line was from the stone or the drill bit.
So I’m guessing it’s a pretty hard rock whatever it is. I guess at least a 7 on the Mohs scale which is great. I can’t wait to get a saw and slab this thing.
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Post by RocksInNJ on Nov 22, 2019 21:12:36 GMT -5
Do you have access to muriatic acid? That would be a better test than vinegar. Streak is a good indicator. Hardness would also be a good clue. You can scratch calcite (3 on Mohs) with a knife (5), but not feldspar (6+) or quartz (7). It is difficult to ID a rock by picture, especially one that has been in water. Even so, without other evidence, I would vote quartz for now. I wouldn’t even know where to look for muriatic acid.
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Post by greig on Nov 23, 2019 11:19:22 GMT -5
Hardware or big box store have muriatic. Usually, it is a bit cheaper from swimming pool supply places. Only thing to say is stay safe. Use it outside, avoid getting on skin or eyes, etc. Keep away from kids or pets.
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Post by RocksInNJ on Nov 23, 2019 12:01:36 GMT -5
Hardware or big box store have muriatic. Usually, it is a bit cheaper from swimming pool supply places. Only thing to say is stay safe. Use it outside, avoid getting on skin or eyes, etc. Keep away from kids or pets. Many thanks. I’ll have to check into it.
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