Streak test question

[G Freeman]

Got a quartz rock with something looks like gold so I did a color mark on my stone and it was yellow shiny so I used 22 kt acid and the yellow mark did not fade so I sent it to assayer and he said no precious metal in my rock. So what I am trying to find out if there is another metal that makes yellow shiny color streak on stone other than gold and that will stand up to the gold acid test. Also refinery never did refine my rocks and assayer is going to send them back to me. Thanks.

 

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[Hoser John]

No such thing as 22 kt acid. Did you use nitric-technical grade---reagent---or utechnic lab grade?? Color mark as in rubbing against unglazed tile and putting acid on it?John

 

[Jason in Enid]

No such thing as 22 kt acid. Did you use nitric-technical grade---reagent---or utechnic lab grade?? Color mark as in rubbing against unglazed tile and putting acid on it?John

Yes there is a 22K test. It's part of a kit used by jewelers and gold scrappers to test for content. It's basically different strengths of acid. If the streak doesn't dissolve in a few seconds, it's at least as pure as the testing liquid. IE... if you streak a ring and put acid drops on the streak, 10K won't affect, 14K won't affect, 18K won't affect, but 22K dissolves it, then you know you have gold somewhere about 18K in purity.

Yes, there are other metals that won't be affected. I know that aluminum won't be touched and my coin dealer told me there are other metal that will also give a false positive.

 

[G Freeman]

Yes Hoser John, bought the gold acid testing kit with acid in different bottles to test for 14 18 and 22kt testing solution for stone color mark. Thanks.

 

[G Freeman]

Yes there is a 22K test. It's part of a kit used by jewelers and gold scrappers to test for content. It's basically different strengths of acid. If the streak doesn't dissolve in a few seconds, it's at least as pure as the testing liquid. IE... if you streak a ring and put acid drops on the streak, 10K won't affect, 14K won't affect, 18K won't affect, but 22K dissolves it, then you know you have gold somewhere about 18K in purity.

Yes, there are other metals that won't be affected. I know that aluminum won't be touched and my coin dealer told me there are other metal that will also give a false positive.

Thanks Jason. Yeah I tested with 18Kt and yellow mark was not affected and stayed. Ruled out Pyrite Mica and Galena as they do not have a yellow shiny streak or mark . So I was just wondering what other metal can give me this mark and still stand up to the acid. All the research I have done pyrite is the culprit to look for as many have been fooled by this. I am supposed to receive a assay report Monday from them and can't wait to see what they say the gold looking metal is as I have not been able to find it other than gold for a yellow shiny mark.

 

[Hoser John]

To dissolve gold it must be a differing quanity of aqua regia(nitric/hcl mix) and a simple set of gold pins easily determines that % kt non destructively. A simple knife/nail test works nicely on a sample as ifn' it cracks,crumbles or goes crunch it ain't gold vs expensive dangerous acid mixtures for simple is/not ID-John

 

[G Freeman]

To dissolve gold it must be a differing quanity of aqua regia(nitric/hcl mix) and a simple set of gold pins easily determines that % kt non destructively. A simple knife/nail test works nicely on a sample as ifn' it cracks,crumbles or goes crunch it ain't gold vs expensive dangerous acid mixtures for simple is/not ID-John

Thanks John, I understand your answer but maybe I did not word my question right because the main thing I wanted to know is what metal other than gold makes a yellow shiny mark on the stone.

 

[aussco999]

Hey G Freeman If your getting blank assays for precious metals, then I doubt what you're seeing in your quartz is a metal. Even an incompetent assayer can produce some precious metal numbers if you have visible gold in the ore. More than likely it's one of the yellow minerals in the sulphide or sulpho-salts family like; orpiment (As2S3), sphalerite (ZnS) or even one of the anhydrous silicates like chrysolite (Fe2SiO4). These minerals and probably a few more will streak a yellow color. Plain old pyrite (FeS2), produces a black streak. It sounds like the 22k acid test confused you even more, but you are probably not aware of the fact that most of the sulphide minerals are refractory in nature. Meaning, they're impervious to both acid and alkali leaching. One of the few exception to this statement is the recovery of copper with diluted sulfuric acid. Regarding a proper mineral streak test, it's always done on a fresh face (break and expose a new mineral surface) on unglazed tile. The back side of a cheap 4”x 4” bath tile from Home Depot works perfectly. You said that you “did a color mark on my stone”, which I'm guessing is the glass glazed or the Arkansas type stone that came with your gold testing kit. This stone will give you good results when dealing with most metals, but a false-positive result for checking minerals. You need to use an unglazed tile for a proper mineral streak test. And finally, never send a mineral sample in for assay work based on a streak test alone. A huge waste of money. There are too many other simple tests you can easily preform in the field before spending hard $$$ for an assayer to tell you “nope'. Check out “Duke's Mineral ID Manual”. I think it's a free PDF download on the web. I think the complete manual covers identifying about 44 metals/minerals by streak, hardness, crystal structure, chemical and blowpipe testing. For about the price of a couple assays, you can gear up enough to ID all of the “money making” metals and minerals in the field. Just my opinion and experience. Good luck, John

 

[G Freeman]

Hey G Freeman If your getting blank assays for precious metals, then I doubt what you're seeing in your quartz is a metal. Even an incompetent assayer can produce some precious metal numbers if you have visible gold in the ore. More than likely it's one of the yellow minerals in the sulphide or sulpho-salts family like; orpiment (As2S3), sphalerite (ZnS) or even one of the anhydrous silicates like chrysolite (Fe2SiO4). These minerals and probably a few more will streak a yellow color. Plain old pyrite (FeS2), produces a black streak. It sounds like the 22k acid test confused you even more, but you are probably not aware of the fact that most of the sulphide minerals are refractory in nature. Meaning, they're impervious to both acid and alkali leaching. One of the few exception to this statement is the recovery of copper with diluted sulfuric acid. Regarding a proper mineral streak test, it's always done on a fresh face (break and expose a new mineral surface) on unglazed tile. The back side of a cheap 4”x 4” bath tile from Home Depot works perfectly. You said that you “did a color mark on my stone”, which I'm guessing is the glass glazed or the Arkansas type stone that came with your gold testing kit. This stone will give you good results when dealing with most metals, but a false-positive result for checking minerals. You need to use an unglazed tile for a proper mineral streak test. And finally, never send a mineral sample in for assay work based on a streak test alone. A huge waste of money. There are too many other simple tests you can easily preform in the field before spending hard $$$ for an assayer to tell you “nope'. Check out “Duke's Mineral ID Manual”. I think it's a free PDF download on the web. I think the complete manual covers identifying about 44 metals/minerals by streak, hardness, crystal structure, chemical and blowpipe testing. For about the price of a couple assays, you can gear up enough to ID all of the “money making” metals and minerals in the field. Just my opinion and experience. Good luck, John

Thanks a lot John for the info and that is what I wanted. Yes I was using the black stone that came with my testing kit and you told me things I haven't heard before. As far as the assay company go's they called me today and are going to send my product back and my check too and pay the return shipping. So nothing seems to be lost. I will check Duke's mineral ID Manuel. Just google it right? I am pretty new at this stuff especially when it comes to Hard Rock quartz. Been working this quartz for about 5 months now. Got a lot of silver looking stuff on this quartz too, like on every other piece we get out and assay co said it was Magnesium. Does that sound right? Thanks.

 

[aussco999]

G Freeman: It will take a lifetime to learn everything that you're looking for, so just take one step at a time. At the moment, I don't have access to my hard copy of Duke's Manual, but I think it comes in 3 parts and it's all available as a free PDF download on the web.
Also, don't overlook your local used book stores. I've picked up some great mineral ID books there including an original 1911 pocket handbook copy of Mineralogy, Blowpipe Analysis and Crystallography by M. Butler for only $5. Everything in that 100+ year old book is still valid, except I've replaced the blowpipe testing with a butane micro-torch.
Try not to rely solely on a visual mineral identification. Some are easy to ID by eye like galena and most of the copper minerals, but after that, it gets more confusing. My business partner is a geologist and he often drags a bunch of rocks back for some additional testing. When I'm in Phx, AZ, I often visit the Mining and Mineral Museum. They have a large mineral display, including 100+ different samples of the mineral calcite. None of them look alike.
If your assay said it was Mg in the quartz, then it probably was as silver seldom looks like silver in nature. I once helped an investor walk away from buying a silver mine from some “wide-eyed people” that had a bunch of silver colored metal in their quartz. It was only antimony. Big price difference.
Congrats on getting your ore and check back from the assayer. That has never happened to me,,, never,,, ever. Bottom line is, you just may have a quartz vein with little or no value, but I recommend that you better educate yourself, and keep on looking.
Good luck,
John

 

[G Freeman]

G Freeman: It will take a lifetime to learn everything that you're looking for, so just take one step at a time. At the moment, I don't have access to my hard copy of Duke's Manual, but I think it comes in 3 parts and it's all available as a free PDF download on the web.
Also, don't overlook your local used book stores. I've picked up some great mineral ID books there including an original 1911 pocket handbook copy of Mineralogy, Blowpipe Analysis and Crystallography by M. Butler for only $5. Everything in that 100+ year old book is still valid, except I've replaced the blowpipe testing with a butane micro-torch.
Try not to rely solely on a visual mineral identification. Some are easy to ID by eye like galena and most of the copper minerals, but after that, it gets more confusing. My business partner is a geologist and he often drags a bunch of rocks back for some additional testing. When I'm in Phx, AZ, I often visit the Mining and Mineral Museum. They have a large mineral display, including 100+ different samples of the mineral calcite. None of them look alike.
If your assay said it was Mg in the quartz, then it probably was as silver seldom looks like silver in nature. I once helped an investor walk away from buying a silver mine from some “wide-eyed people” that had a bunch of silver colored metal in their quartz. It was only antimony. Big price difference.
Congrats on getting your ore and check back from the assayer. That has never happened to me,,, never,,, ever. Bottom line is, you just may have a quartz vein with little or no value, but I recommend that you better educate yourself, and keep on looking.
Good luck,
John

Assay report also said I had Yttrium and iron in my quartz rocks I sent them but never did say what the gold looking stuff on the rocks was as Yttrium, iron and Magnesium does not give a yellow mark on anything. After looking up these things on Mindat .org Yttrium and Magnesium are silver color on the rocks. Could the gold looking stuff be iron? I have called them trying to find out and the girl that works there does not have that info. Thanks.

 

[aussco999]

Hey G Freeman: A standard precious metal assay doesn't normally report other base metals, so I'm guessing your assay was based on some sort of multi-element mass-spec analysis which would report iron percentages and rare earths in PPM/PPB. If that's the case, check the sulfur (S) percentage. Anything over about 4% to 5% indicates a sulfide mineral and that's probably your yellow streak. Look for another high percentage base metal which might give you a better idea what sulfide combination is in your ore. Extracting Yttrium is a complicated leaching process and unless your ore has it in high percentages, it's probably not worth the time or expense. I think China and Brazil controls most of the world market anyway. Put a little heat on the yellow mineral (do it outside), for a few seconds with a small torch and see if the yellow turns a darker color. Don't breath any fumes in case it's something bad, like arsenic and then try another streak test. The process of elimination has begun. Good luck, John