Types of Rocks That Contain Gold (and the Ones That Rarely Do)
Gold shows up in a handful of rock types again and again. Learn which rocks are worth checking, what the gold-bearing versions look like and which common rocks are usually a waste of time.
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Gold can turn up in almost any rock if the right fluid passed through it, but in practice it favours a small group of settings. Knowing them lets you scan a hillside or a creek bed and quickly decide where to spend your time.
One thing to keep in mind before we start: the rock type alone is never enough. What matters is whether hot, gold-bearing fluids moved through it. A plain slate is just a slate. The same slate cut by rusty quartz veins next to an old mine is a different story.
Quartz veins
Quartz is the most common host for visible gold. It is not a rock type as such but a mineral filling cracks in other rocks. Gold-bearing quartz is usually stained with rust, full of small cavities or banded, while barren "bull quartz" is clean, milky and massive.
Read our full guide on why gold is found in quartz for the reasons behind this and more tips on spotting promising veins.
Greenstone
Greenstone is an old volcanic rock, mostly basalt, that has been altered by heat and pressure into a dull green rock rich in chlorite and epidote. Greenstone belts in Western Australia, Canada, Africa and Brazil host many of the world's biggest orogenic gold deposits.
Why green rock? Basalts are rich in iron. When gold-bearing fluids react with iron-rich rock, sulfur in the fluid combines with the iron to form pyrite, and the gold loses its chemical carrier and drops out. Iron-rich rocks act like a chemical trap.
Schist and slate
These metamorphic rocks started as mud and fine sand on old sea floors. Under pressure they developed a strong layered fabric that splits into sheets. In places such as the Victorian goldfields of Australia and the Otago region of New Zealand, quartz veins cutting through slate and schist are the main gold source.
Look for quartz veins running across or along the layering, especially where the rocks are folded or crumpled.
Iron-stained rock and gossan
A gossan is the weathered, rusty cap that forms when sulfide minerals near the surface break down. It is usually a mess of red, brown, yellow and orange iron oxides, often with a spongy, cellular texture where sulfide crystals have dissolved.
Gossans do not always mean gold, because many sulfide bodies carry only iron or base metals. But they mark places where sulfide-rich fluids were active, and early prospectors tested almost every gossan they found. Some famous deposits were discovered exactly that way.
Conglomerate
Conglomerate is a rock made of rounded pebbles cemented together, in effect a fossil gravel bed. If the original river carried gold, the conglomerate can carry it too. The Witwatersrand Basin in South Africa, the largest gold field ever discovered, is made of ancient gold-bearing conglomerates.
On a hobby scale, cemented gravels in old river terraces can hold gold that the modern creek has never touched. Breaking them down and panning the material is hard work but sometimes rewarding.
Granite contacts, not granite itself
Granite has a reputation as a gold rock, but solid granite rarely carries much gold. What matters is the contact zone, where hot granite intruded into older rocks. Fluids released as the granite cooled moved into the surrounding rock and, in places, deposited gold in veins along that margin.
When you see granite on a geological map, look at the edges, not the middle.
Volcanic rocks near old hot springs
Rhyolite, andesite and volcanic breccia can host epithermal gold where ancient hot spring systems were active. Clues include bleached or clay-altered rock, banded quartz, chalcedony and sinter, a layered silica deposit left by hot springs at the surface.
Black sand and heavy mineral layers
Not a rock, but worth adding. In streams and beaches, heavy minerals such as magnetite and ilmenite collect with gold. A layer of black sand in a creek bank or on bedrock is a natural concentrate and always worth a test pan.
Rocks that rarely hold gold
To save time, these are usually poor bets on their own:
- Limestone and marble far from intrusions or faults. Exceptions exist, such as skarns and Carlin-type deposits, but the gold there is usually invisible.
- Young volcanic ash and pumice with no sign of alteration.
- Fresh, unaltered granite away from its contacts.
- Sandstone with no veins or iron staining.
A quick checklist for any rock
Before you put a rock in your bag, ask:
- Is there quartz or another vein mineral?
- Is there rust, boxwork or sulfide?
- Is the rock altered, bleached, green or clay-rich compared with the fresh rock nearby?
- Is there a fault, contact or fold nearby?
- Has gold been found in this area before?
Three or more "yes" answers make a sample worth testing. If you see something yellow, run through our pyrite vs gold checks before you celebrate.