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You need to know something about how gold deposits occur to understand which rocks to look for when prospecting. Alluvial deposits are made by water running over rocks in rivers and streams, while gold veins or reefs are deposits of gold left by geological processes in large bodies of rock. The former are secondary deposits, while the latter veins and reefs are primary.
Five rocks to look for when gold prospecting are quartz, granite, basalt, schist, and slate. Gold is deposited in them through volcanic hydrothermal activity or rainwater solutions containing minerals and heavy metals like gold. Gold drops out of the solution and is deposited in cracks and crevices.
It’s hard to find gold in significant quantities, but you can improve your chances by knowing where to look and what to look for. Panning for gold in a mountain creek or on a sandbar in a river can be exciting when you catch that first bright glint in the sunlight.
This article explains what to look for in rocks when prospecting for gold, the five kinds of rocks commonly associated with gold, and how to tell if a rock has gold in it.
If you are interested in checking out the best tools and equipment for gold prospecting you can find them by clicking here (Amazon link).
What To Look For In Rocks To Find Gold?
You need to learn to read the natural rocky landscape. Alluvial deposits are always associated with water flow and consist of eroded rocks and soils that form sediments in low-lying spots. Quartz stones in alluvial deposits are a sign there may be gold present.
If the surrounding area shows signs of water runoff, such as old streams or river beds, or if you are in a valley surrounded by mountains close to a flowing creek, gold could have been washed down from higher up.
Gold commonly occurs in veins of quartz rock or placer stream gravel, but given that quartz is the most plentiful mineral on the Earth’s surface, this doesn’t say much.
It is found in all three basic rock types: igneous, metamorphic, and sedimentary. Quartz is distributed everywhere – in valleys, rivers, and streams and on hillsides and mountain tops.
It helps to know the regions in your country in which gold has already been found to narrow down the number of areas in which to search. The geology of the site is important too.
One place in which gold occurs may differ geologically from another in which it also occurs. It is not the composition of the rock so much as the geological processes that took place there that determine whether there are gold deposits.
Rocks that are lighter in color than the surrounding rock, and look out of place can indicate gold. The discoloration is caused by acidic minerals in gold-bearing rock that wash out and bleach those nearby. You should also look for chunks of quartz and quartz pebbles or veins in the area.
Quartz is usually white but can also be clear. It can be white with rusty, reddish markings when stained by iron oxides. Veins of quartz are generally clearly visible in cliffs and rock faces. Water can wash gold particles from these places into nearby streams and rivers.
Black sand is associated with the presence of gold but doesn’t guarantee it. It is very heavy and contains a lot of heavy metals and minerals. The presence of rock fractures is key because they allow mineral solutions to flow around and react with the rock.
TIP: You can pan for minerals or dig through the dirt, but by far, the easiest way to find gold or other gemstones is to search in the gravel beds of dried-up rivers. Check out the article below if you want to find out more:
8 Tips On Finding Gemstones In Nature (Rivers & Creeks)
What Other Rocks Are Found With Gold?
Calaverite and sylvanite are gold-bearing minerals. Copper-bearing rocks known as copper porphyries may contain gold or are associated with its presence. These are most common in specific types of igneous rock.
Placer deposits only occur in sedimentary rock because the gold particles are moved in the silts, sands, and gravels by water.
Gold can occur with just about any other type of rock because the composition of the rock isn’t the essential factor. It’s the geothermal processes that have happened there that matter.
Minerals that are associated with gold deposits are:
- magnesium ferric, a dark mineral-tinged with black or red;
- iron, lead, magnetite, and pyrite, which are heavy like gold and also form around gold-bearing quartz veins;
- chalcopyrite or Fools Gold which is often found near real gold;
- malachite is a deep green stone that is often found near gold deposits.
How Do You Know That A Rock Has Gold In It?
You can scratch a rock against a piece of unglazed ceramic like the back of a kitchen tile to see if it has gold in it. Genuine gold leaves a gold streak while fool’s gold leaves a greenish-black one.
Gold isn’t attracted by a magnet, while fool’s gold is because it has a high iron content. If you put a rare earth magnet next to the rock and nothing happens, chances are it contains gold.
Also, close inspection of the rock with a jeweler’s loupe will show a distinct yellow color and non-crystalline structure in the case of genuine gold. Iron pyrite or fool’s gold has a pronounced crystalline structure.
TIP: Natural pyrite is usually known as fool’s gold but even pyrite fakes can be sometimes spotted. Check out the main differences between real and fake pyrite in the article below:
Real vs. Fake Pyrite: Focus on These 7 Differences
What Rocks To Look For When Gold Prospecting
It helps to know a bit about rocks when seeking gold. Granite, basalt, schists, slate, and shale are rocks to look out for when gold prospecting. Large quantities of iron oxides such as magnetite, ironstone, or hematite in an area can also indicate the presence of gold.
Rock 1 – Quartz Veins
Quartz veins are closely associated with the presence of gold and are visible in rock faces and cliffs in the surrounding area. Weathered chunks of quartz lying on the ground and smaller quartz stones and pebbles in rivers and streams or on their banks are also signs.
Gold is often deposited together with quartz, amethyst, and other heavy metals by igneous volcanic hydrothermal activity.
Rock 2- Granite
Granite is an igneous rock where gold washed down from hillsides and mountains can accumulate because it keeps the heavy gold particles from going any further. Thus granite rock deposits with water running through them are a good place to find secondary gold.
When prospecting for gold around granite bedrock, it’s best to look in cracks and crevices where gold may accumulate.
When quartz and iron occur with granite in a known gold-producing region, this may be a sign that gold is nearby. Iron oxide is a reddish or black color and can be identified using a magnet.
Rock 3 – Basalt
Basalt is a dark volcanic rock formed from molten lava. If you break open a piece of basalt with a rock hammer and see a greenish color in it, this is a sign that the area may have gold. The magma that formed the basalt may have contained gold.
TIP: When magma erupts from a volcano, it forms extrusive or volcanic rocks on the surface. Check out the most common rocks you can find near volcanos in the article below:
Ten Most Common Types of Rocks You Can Find In Volcanoes
Rock 4 – Schist
Schist is a metamorphic rock made mostly from micas that glitter in the sun. Micas are flaky, sheetlike minerals that include dark green chlorite, silvery muscovite, metallic gray graphite, white grey or green talc, and black or brown biotite. Schists often contain quartz in addition to mica minerals which increases its strength.
Layers of decomposing schist can hold alluvial gold. Schist comes in many colors and textures. Gold occurs together with quartz reefs in schist. Reefs are veins in the rock. However, gold deposits in schist are typically small and irregular, making it difficult to predict where they can be found.
Rock 5 – Slate
The Carolina Slate Belt is known for its gold production. According to a US Geological Survey Report in 2012, it has produced between one and more than fifty metric tons, depending on the size of the mining operation.
Gold can be found in slate slabs in some places because the heavy gold particles can be deposited in the layers as water runs through them.
BTW: Do you want to know more about rock and mineral identification? The books listed below are the best ones you can find on the internet (Amazon links):
- Smithsonian Handbooks: Rocks & Minerals
- Gemstone & Crystal Properties (Quick Study Home)
- Ultimate Explorer Field Guide: Rocks and Minerals (National Geographic Kids)
Finding gold has never been easy, but there are signs to look for to improve your chances. Quartz veins or chunks, the presence of greenish-looking copper or rusty iron oxide, iron pyrites, and lighter colored rocks that stand out can help you decide where to pan or dig.
TIP: Having the right tools on hand will allow you to worry about your hobby more than the tools themselves. Check out the best hammers, chisels, and more for your adventures in nature:
Recommended Rock Hammers, Picks, Chisels & Bars For Rockhounding