One of the prized finds out there, for both collectors and prospectors, is the fabled specimen of gold and quartz. One of the most common signs of the mother lode, these nuggets have fascinated humans for millennia. But first, you need to make sure you have the right thing!
So, let’s get into figuring out the ins and outs of gold-bearing quartz specimens!
Why Does Gold Occur in Quartz?
Even if prospecting isn’t your exact get-down, you probably know about gold in quartz. It’s a common trope and the formation has a beauty of its own.
A lot of beautiful nuggets have been destroyed for their gold content over the years. But why does it happen this way?
It turns out that humble quartz (or silica) is one of the last minerals to cool down during hydrothermal action, creating a porous mass of quartz.
Gold has long been found in the fractures and cracks of these stones and can occur in large veins during hard rock mining. Its presence is usually explained as being due to gold-bearing hydrothermal fluids running into the cracks and depositing minuscule amounts of gold over a long, long time.
That’s was about as close as anyone’s ever been to explaining it. And a lot of people have studied it.
After all, a prospector will move hundreds of pounds of gravel just to get a few flakes and a small nugget of gold… now scale that up to mining companies with billion-dollar R&D budgets.
A recent study in Brazil actually posits a new solution: nano-particles of gold held in suspension begin to collide with each other and form a mass inside the fracture. Eventually, this fills in the quartz fracture.
Regardless of the reason for its formation, gold-bearing quartz is an important economic resource so further study will undoubtedly bring the matter fully to light.
How to Be Sure It’s Gold
There’s a problem with finding gold in quartz: pyrite likes to occur in the same places.
While attractive, “Fool’s Gold” isn’t expensive stuff. It can make for visually interesting specimens, especially mixed with other minerals, but gold it is not. There are a few other minerals that can also look very similar to gold and occur in similar formations.
Fortunately, at-home testing isn’t hard.
You have three basic methods at your disposal:
- Magnetic Testing- Touch a magnet to the specimen. Pyrite is magnetic, gold isn’t.
- Density- Measure the volume and weight of a gold-bearing stone. Quartz has a density of 2.65 g/cm³, while pyrite sits at 5 g/cm³. Gold will be 19.3g/cm. Without exact measurements, this test is more promising than conclusive, but gold will stick out like a sore thumb if you have another, similarly-sized piece of quartz for comparison.
- Scratch/Streak Test- Pyrite and chalcopyrite scrape glass, gold won’t. If your specimen has an outcropping that’s convenient try scratching glass with the “gold” portion to find out. Actual gold should leave a golden-colored streak if rubbed against an unglazed ceramic tile as well, compared to the black pyrite leaves.
If the above tests look good, then you most likely have gold on your hands.
If you don’t mind destroying the specimen you can also acid test it.
Vinegar is the only thing I’ll recommend for someone with no chemical experience and PPE. Just fill a jar, drop the specimen in, and go to bed. It’ll take several hours, but quartz dissolves in acidic solutions, as do pyrite, chalcopyrite, and many other gold mimics.
Gold doesn’t dissolve in anything reasonable, if it’s still there in the morning you have gold.
I’d think hard before going into that test. You can easily destroy the value of your piece by getting over-eager to figure out what it is.
What is Gold in Quartz Worth?
Gold prices change daily. Hourly, even. You can check a price index, I use APMEX to get a good idea if you know how much gold is in the specimen. Keep in mind that a lot of specimens that seem to have a lot of gold may only have a few scant grams while being visually impressive.
The gold in your piece is most likely in the 20K range or around 83.3%, but some places like Australia regularly have higher purities in their hard rock ore.
Impurities can include silver and copper, but lead is another common one. It’s not wise to refine gold at home unless you really know what you’re doing. The idea of playing with a mixture of nitric and hydrochloric just doesn’t appeal to me most days, and the chemical precautions alone will take some time to learn.
Depending on the refiner you may see 70-90% of the gold’s spot price returned to you. That can be a good bit of profit, depending on what you have.
But often the price of gold-bearing quartz is more than the value of the gold.
Specimens are highly prized raw once you’ve got all the dirt out. If there’s a lot of surface gold on a piece it may end up selling for twice the actual spot value of the gold if you can find a buyer.
I recommend having promising specimens appraised at a rock shop, they’ll know better whether the piece has extra value as a specimen than a jeweler in most cases. Some will buy them from you for a wholesale price before they resell them or you can take the chance on doing it yourself through a platform like Etsy or eBay.
Here’s the thing: gold-bearing quartz is pretty rare. Humanity’s lust for the yellow stuff tends to not leave behind very much material so the specimens are going to be worth more. It actually makes very attractive jewelry in my opinion, and small bits cut perfectly around a tiny vein are amazing.
If you cut stones and are confident you can do it without scraping off all the gold… you can also cut them into cabochons or just polish the surface to increase their value. This isn’t a job for amateurs, and I’d seek out some mentorship before trying even if you’re a decent lapidary.
A very few specimens are heavily carved and can be worth even more. If the artist is well known, then a specimen with a few grams of gold can end up being worth thousands of dollars more than the actual gold contained within.
Bottom line: it depends entirely on the specimen, but at the bare minimum, you should be able to retrieve 75%+ of the current spot value of the gold contained within.
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