People have been searching for gold for thousands of years. You have more chances of finding gold when you know about the rocks that contain gold.
Sedimentary, metamorphic, quartz, granite, and igneous rocks can have gold. You need to learn specific rock types in these classes to mine at locations with more chances of finding gold. Gold comes from the deeper layers with hydrothermal activity.
What Are the 5 Rocks that Contain Gold?
There are five rocks that are known to contain gold. This is a helpful guide for all beginner gold diggers.
- Metamorphic Rocks
- Sedimentary Rocks
- Igneous Rocks
- Quartz Rocks
- Granite Rocks
1. Metamorphic Rocks
It is hard to find gold in metamorphic rocks because they change shape under high pressure.
All the gold in the rock is packed inside the dense layer of minerals.
The gold is not visible on the surface because it is packed inside the deeper layers of the rock.
Because of their low concentration, many do not want to get gold from the metamorphic rocks.
We use different units of concentration for gold in the metamorphic rocks.
PPM and PPB are the units to measure the concentration of gold in Metamorphic rocks.
PPM is parts per million. One PPM means there is part of the gold in a million parts of the substance.
PPB is parts per billion. One PPB means there is one part of the gold in billion parts of substance.
Metamorphic rocks have One part per million to 20 parts per billion concentration of gold in the metamorphic rocks.
It is not cost-effective to extract gold from rocks with such low concentrations.
You may have to spend more money to extract gold than the price of gold you get.
Many prefer Sedimentary rocks instead of metamorphic rocks to mine for gold because they have higher chances of making profits.
2. Sedimentary Rocks
Sedimentary rocks contain more gold as compared to metamorphic, igneous rocks.
Metamorphic and igneous rocks can face erosion in water.
They turn into small sediments as they move in the rivers.
Gold reaches these rocks through hydrothermal activity.
Water from the deeper layers of the earth comes inside the rock veins and deposits materials there.
Gold also comes with them. As erosion breaks these rocks, they carry gold to the sedimentary rocks.
People find gold in higher concentrations at the river beds.
You may have seen videos of people using a pan to filter the river water.
This method is known as panning. It is one of the best methods to find gold from the sediment layers of rivers.
There is no need to mine for gold if you can find nuggets of gold in the river.
Gold is heavier than sand and other rocks.
It will stay at the center of the pan during panning.
Some lakes also have layers of sedimentary rocks.
These are also perfect for gold hunting.
3. Igneous Rocks
Some igneous rocks can have more gold than sedimentary rocks also.
Igneous rocks form when minerals cool at the surface of the earth.
The heat melted these minerals in the deeper layers of the earth.
Igneous rocks are also known for metal inclusions.
These rocks can have different types of metals.
Gold is one of the metals people find in igneous rocks.
They do not occur in the deep layers like the metamorphic rocks.
You can see them through the transparent crystals of the igneous rocks.
The gold will show itself due to its shine in the igneous rocks.
When the igneous rocks form due to the cooling process, veins form in them.
These veins become channels for hydrothermal water.
Hot water from the hydrothermal activity passes from these channels and deposits minerals and metals in them.
Gold also comes with hydrothermal activity in the igneous rock veins.
Gold in the river beds also comes from the igneous rocks when these rocks break due to water erosion.
You may find small nuggets of gold in the sedimentary rocks.
It is possible to find large chunks in the igneous rocks.
4. Quartz Rocks
Quartz forms when the Silicon atoms react with Oxygen.
This reaction occurs at high temperatures and pressure.
Silicon comes from the other igneous rocks.
Silicon is also available in free form in the earth’s crust.
Quartz is abundantly available on all continents.
We will discuss the details of the chemical aspects of the Quartz.
- Quartz forms when one Silicon atom reacts with two oxygen atoms to make SiO2.
- It is not a single molecule as SiO2 forms a chain structure where all the Silicon atoms form bonds with more than two oxygen atoms. There are repeating units of SiO2.
- These rocks have a tetrahedral structure. Four Oxygen atoms surround each Silicon atom.
It is better to learn about the physical properties of the Quartz crystals. Some physical properties are listed below.
- Pure Quartz crystals are colorless with a milky appearance. Metal and mineral impurities give it different colors.
- You can find Quartz in Brown, Pink, Red, Green, Yellow, and Purple colors.
- Quartz reacts to light in the same way as glass.
- Quartz crystals are resistant to damage from most chemicals.
- Hydrofluoric acid with high acid strength can dissolve Quartz.
5. Granite Rocks
Granite is a rock that forms when different melted minerals cool together.
Granite is famous among rock miners because it can contain gold in the veins.
You can find granite in many colors.
You can find gold in pink or gray granite frequently.
Granite occurs in the form of large structures.
These are perfect for gold deposition.
Most types of granite stones consist of Mica, Feldspar, and Quartz.
Silica and Alimuna make up most of the granite structure.
Most granite rocks have 72.04 percent Silica and 14.42 percent Alumina.
You can find granite in stone-like masses in the mountain regions.
You can dig deep into the granite rocks to find the gold veins.
People who sell granite building materials stumble upon gold nuggets sometimes.
It is an advantage of the granite material cutting business.
How to Identify Rocks that Contain Gold?
Most rocks do not show the presence of gold. Some rocks give hints about gold.
It is easier to find gold in transparent stones.
Quartz crystals have high transparency.
You can see through the crystals.
Gold will appear in yellow inside the Quartz crystals.
Most gold miners look for large Quartz rocks with visible gold particles.
It is a sign that there is more gold in deeper rock layers.
You can get the estimate of gold concentration in the rock when rocks are not transparent.
You can take a sample rock and break it to find the amount of gold in a small piece of rock.
It is easy to calculate if you can extract gold and make a profit from the process.
You can extract gold from the ore when the process costs less than the gold price you got from extraction.
Not Just Rocks but Minerals Can Contain Gold
Many minerals have gold as an impurity.
These minerals can have small pieces of gold in them.
You can break mineral crystals to extract the gold.
Some minerals have gold in their chemical structure.
Calavarite and Sylvanite are two minerals with gold in their mineral structure.
These minerals can have up to forty-three percent gold.
Sylvanite and Calavarite have the same chemical structure with one difference.
Calavarite has more than 13 percent silver replaced by gold atoms.
You can learn the differences in the appearance of gold and pyrite.
Some people break a large rock to find pyrite instead of gold.
You can save energy and time when you know the difference in the appearance of gold and pyrite.
Conclusion
We can conclude that many Rocks contain gold.
It is easier to find gold in the rocks with high transparency.
You can extract gold from the opaque stones by checking the concentration of gold using a small sample.
Minerals can also have gold in high concentrations.
Some minerals have gold in their chemical structure.
Sedimentary rocks can have small gold pieces in the river beds.
Igneous rocks can have gold in the veins of the crystal structure.