Unsure if Gold or Pyrite

[mikeparker]

I recently found a bunch of quartz in a local stream. It has a lot of gold flakes on it, but I cannot determine if it is gold or pyrite. Attached is a picture of one of the rocks. I have scraped a lot of the gold off of the rocks and it is quite shiny. No nuggets.

 

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[AU_Solitude]

Gold colored mica.

 

[snakejim]

Hit it with a hammer. If it's gold it mashes like lead. If it's pyrite it shatters like glass.

 

[mikeparker]

Hit it with a hammer. If it's gold it mashes like lead. If it's pyrite it shatters like glass.

It is really ingrained in the quartz, and I've had to scrape it off with a dull knife to get the dust. If it were gold, it would come off more easily?

 

[Underburden]

How does it react in a pan / water.
Swirl easily with little effort or does it hang back.
Best investment you can make is a cheap 10X loupe to see for yourself.

Hope it's gold for you.
Bob

 

[Underburden]

Double post

 

[AU_Solitude]

Gold doesn't just scrape off - take one of the flakes you scraped off and if you break it apart with the tip of a pin or nail it's just mica or pyrite. I have found similar looking rocks and its just gold colored mica. It will get the heart pumping because the color can seem right even out of light.

 

[robert2b]

Certainly looks like Mica. I had one guy try and sell me a mine saying that it was full of gold. When I looked at the rocks they were full of small flakes of gold colored mica. I had to break the bad news to him. Like the man above said, put some in a pan and see what it does.

 

[DizzyDigger]

Mike, to make absolutely sure it is Mica you can always
crush up a piece and pan it out.

 

[tabu]

Try roasting some-- mica would hardly be affected. Pyrite would change color and give off acrid smoke like burning sulfur and eventually leave a dark magnetic residue (iron oxide). You may try putting some bits on a small glass bottle with some nitric acid (or dilute nitric acid heated in a stainless steel pan) and if it's pyrite you'll see a vigorous reaction-- dark brownish (nitrogen oxide) fumes and the liquid turning greenish (iron nitrate solution) with albuminous residue (sulfur). Take the usual safety precaution-- do it in open air or under a hood. If gold is present it will remain unaffected and literally "cleaned" off the pyrite that might be concealing it. If the gold is alloyed with silver, the superficial silver exposed to the acid will dissolve forming colorless silver nitrate and leaving the gold more gold-like in color.

tabu

 

[tabu]

In the gold-rush jungle hinterlands of the island of Mindanao, Philippines the typical artisanal miner has to make do with whatever tools he has and oftentimes resort to improvisation. I presume this is quite true in Africa as well as in South America.

For example, if the banned toxic amalgamating agent mercury is not available the ore (has to be high-grade) after being ground to the desired fineness using an improvised rod mill (takes around 8 hours for a 40-kg bag) is carefully panned to get the desired concentrate which could be a mix of gold particles, sulfides and other heavier materials.

Again, in the absence of mercury, the concentrate is "cooked" in a stainless steel bowl (readily available and particularly unaffected by nitric acid) on a wood fire and using nitric acid (the dilution dependent upon the "cook" or miner). One learns not to stay in the downwind as the nasty, corrosive brownish red NOx fumes billows in the breeze. When the concentrate is "cooked", i.e,. no more fumes, it is carefully washed with water from a nearby stream and gently panned. The lighter materials including the sulfur (like regurgitated infant milk) are removed with further washing.

The remainder is an agggregate of fine to coarse gold and other acid-resistant constituents like magnetite. The gold may not look the typical gold-- it could be off-colored like reddish dirty with some black "varnish" but nevertheless gold with its typical high specific gravity. Placed on a clay dish with a little borax and "cooked" again using a reducing flame from a DIY gasoline torch, the golden particles melt and coalesce and lose their dirty "overcoat".

The size of the final yield (still unrefined) ranges from a centavo (penny) to a small medallion (if you're lucky). Big or small they all look pretty. Gold!

tabu

 

[Scubaman2]

Looks to be pyrite. You do have some mineralization in that quartz. Would be worth crushing to see if there is any gold associated with the pyrite. They can run together.

 

[IDdesertman]

I would guess that 99.9% of the time, if you can "see" some gold in a stream, it is not gold. Good info posted above, scrape it with a pocket knife and see how it acts.

Gold vs. Pyrite. The Difference Between Gold and Iron Pyrite

 

[tabu]

View attachment 973479

I would guess that 99.9% of the time, if you can "see" some gold in a stream, it is not gold. Good info posted above, scrape it with a pocket knife and see how it acts.

Gold vs. Pyrite. The Difference Between Gold and Iron Pyrite

View attachment 973471View attachment 973477View attachment 973481View attachment 973482View attachment 973483


I agree. It's either fool's gold or mica for most of the time. Looks alone can be deceiving for weekend miners.

Here's some pictures of two rock fragments taken from an outcrop. You can see the difference in color within the same samples. Obviously the varying shades of rust color point out to different degrees of exposure to water and air with the resultant decomposition (basically by sulfuric acid and oxygen) and physical alteration of the ores. Some freshly exposed portions reveal tantalizing bright, shiny and yellow streaks and discrete patches.

Sorry guys-- these two rock samples are pyrite ores. Of course, they contain other "contaminants" and most likely gold. But the gold are too small to be appreciated by the average miner. The gold atoms are locked within the pyrite crystal and one will need an electron microscope to confirm their presence and the economics of recovery are beyond the reach of most everybody.

A retired mining engineer who worked in the goldfields of South Africa once told me offhand years ago that based on his personal experience pyrite or pyritic ore notably in massive configuration are for practical purposes-- barren.


tabu

 

[goldenmojo]

Looks like something I shoveled out of the river on Sunday. Very shiny and looked like a half an ounce glob. I was happy for about two seconds until I realized it was mica. From the pic looks like mica. Smash It