The Beginner’s Guide to Backyard Geology

 

Child splashing water on a sidewalk with rocks and grass
Summer is prime time for aspiring geologists to explore the U.S.’s richly diverse assortment of minerals, rocks and gems – but where do you start?

This guide shows you exactly how to mine your own backyard for treasures and cultivate a lifelong hobby. It’s the perfect mix of fun in the sun and good, old-fashioned learning, so amateur geology is a great way to keep kids occupied throughout the summer, too.

Basic Household Tools to Use for Backyard Geology

Using items you already have around the house, you can set up an entire geological operation in your backyard.

What you need:
• Digging implements, such as a metal spoon and a small shovel
• Gardening gloves
• Magnifying glass
• Sifting pan or kitchen colander
• 1 gallon of water
• Paper towels or soft cloths
• Iron nail
• Magnet
• Small plastic containers
• Notepad and pen
• Sticky labels
• Access to the internet for rock identification (sites like Minerals.net are extremely valuable resources for amateur geologists)
• A basic geology book, like National Geographic Kids Everything Rocks and Minerals or Geology For Dummies

Put all your equipment in a wagon so it’s easy to tote to your dig sites.

Remember: Safety First

Be sure to handle sharp tools with caution when rock hunting in your backyard. Wearing gloves can prevent small cuts while digging up rocks with rough edges. If you or your child accidentally gets a small cut, wash the wound thoroughly with soap and warm water to avoid infection.

How to Choose a Dig Site

There are three basic types of rocks: igneous, sedimentary and metamorphic. Depending on your location, some types are more prevalent than others are.

Igneous rock is formed from molten material. Lava rock, granite and basalt are most common in parts of the U.S. Northwest.
Sedimentary rock is formed from eroded fragments of other rocks and from the remains of plants or animals. This type of rock is where you’ll find fossils, and it forms in areas that used to be underwater.
Metamorphic rock is formed when heat, pressure or the intrusion of fluids transforms sedimentary or igneous rock. These rocks are most commonly found in mountainous regions.

If your backyard has a rocky patch, that’s prime space for digging. Likewise, any place where water runs naturally, such as a stream or river, can make a great dig site.

Rocks and minerals in a stream or water source

Common Backyard Rocks in the U.S.

Some of the most common backyard rocks in the U.S. include:

 

 

 

Granite
Granite
 

 

Basalt
basalt
 

 

Diorite
Diorite
 

 

Obsidian
Obsidian
 

 

Pumice
Pumice
 

 

Marble
marble

 

How to Identify Backyard Rocks

When you’ve collected a healthy set of specimens, run them under clean water. Some might require a little scrubbing! Use your sifting pan or colander if the rocks are small so you don’t lose them.

Pro tip: Clean your rocks thoroughly before you try to identify them. Many rocks are weathered and worn on the outside, so they look ordinary until you crack them open with a hammer. Before you hit a rock with a hammer, wear eye protection and ask an adult to watch.

Washing rocks in a sink with a bucket and scrubbing tools

Look Closely

Look at each with your magnifying glass to identify its characteristics. When you’re done examining a rock, affix a sticky label to the bottom of it (the side with the fewest interesting characteristics) and assign it a number. Write down its characteristics, along with the number you’ve assigned it, in your notepad; you’ll need them to zero in on what type of rock it is later.

Scratch the Surface

Try to scratch each rock with your fingernail, which can help you identify it by its hardness. The harder a rock is, the more likely it is to be valuable; geologists use the Mohs Hardness Scale to gauge rocks. If you can leave a mark with your fingernail, the rock’s hardness is about 2.5 Mohs; if you can scratch it with an iron nail, it’s about 3 Mohs. If you can scratch a rock with glass, its hardness is about 5.5 Mohs. The hardest known substance is 10 Mohs. (Diamonds clock in at 10 Mohs, but you’re not very likely to find one of those in your backyard.)

Test for Magnetization

Run a magnet over the rock to find out if there is any iron in it. This can help you identify rocks such as magnetite or hematite, or even a meteorite.

Compare What You Already Know

Use the internet to find out what kinds of rocks you’re dealing with. Geology.com is a fantastic resource, and it’s packed with hundreds of photos of common – and uncommon – rocks, minerals and gems that you might find in your backyard or on an expedition.

Backyard Geology Tips for Beginners

For most people, it makes sense to start close to home; your backyard could be a treasure trove of great finds. Other tips successful geologists always follow include:

• Document everything. Label all of your rocks, minerals and gems so you can refer to your notes when you find another, similar piece. This also helps you keep track of important characteristics that rocks in your region have, which can help you identify geological patterns in different parts of your city or state.
Clean all your finds thoroughly. Sometimes a grimy outer layer can be tough to remove, and it can prevent you from properly identifying a stone. You may need to put in a little “elbow grease” before you narrow down a rock’s type.
Keep researching. Even if you’ve identified a rock, mineral or gem, you might not be done learning about it. Knowing how a rock was formed, what it was used for in the past, and what it’s used for now can change your whole perspective on what you find.

How to Store Your Rock Collection

Clear, plastic storage cases with several compartments are ideal for storing rock collections. You can label each compartment to match the labels on your pieces, too, and create a chart for the lid for quick identification.

When you discover really eye-catching specimens, you may want to display them. Some people choose to use small shadow boxes, while others pick mounting options and order engraved plates for exceptionally rare pieces.

Some people choose to use a rock tumbler to make their collections sparkle and shine, while other amateur geologists prefer to leave specimens as they found them. Either way, your collection is going to be amazing – it’s just a matter of personal preference.

A labeled rock and mineral collection

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