AHG Geology Badge: Rock Collection, Exploration, and Identification

Rocks are the building blocks of earth's crust.

Igneous rocks are formed when magma cools and hardens.

Sedimentary rocks are formed from particles of sand, shells, pebbles, or other particles (sediment) that "cement" together.  They are typically softer rocks and may crumble.  Sometimes you can see the pebbles or sand, and you may even find fossils in this kind of rock.  

(from Learning About Rocks book)

Metamorphic rocks are formed under the surface of the earth by intense heat and pressure.  These rocks typically have ribbonlike layers and may have shiny crystals from minerals growing slowly over time.

Which rocks would you expect to find in your area?  Which types of rocks would you not expect to find in your area?  Since we are not located in a volcanic area, we would not expect to find igneous rocks.  However, when I traveled cross country a few years ago I picked up some Apache Tears which are obsidian, an igneous rock.  

(from Learning About Rocks book)

You usually do not have to walk far to find a wide variety of rocks.  Take a look around your yard, along a river or stream, or near outcroppings.  Start a rock collection of a dozen different rocks.

Egg Cartons are convenient way to store your rock collection.  Assign each rock a number.  In your nature journal draw a picture of where you found the rock.  Use my FREE Rock Exploration Sheet (which conveniently fits into the top of an egg carton) to answer questions about each rock.  Based on your answers and the location you found your rock, do you think your rock is igneous, sedimentary, or metamorphic?

AHG Geology Badge Rock Collection Identification

Do you see any patterns or correlations between the rocks and where you found them?  For example, rocks you find in or near water are typically smoother than rocks near outcroppings.  

From our Activity Rocks (by GeoCentral) we learned that dolomite, a sedimentary rock used to build roads and make cement, contains limestone which can be dissolved by vinegar.  According to the activity kit, when you place dolomite in vinegar the limestone dissolves and once the vinegar evaporates the limestone reappears as crystals.  Adding a penny creates bluish crystals.

We observed bubbles coming from the dolomite as the limestone dissolved in the vinegar.  The kids then took off outside to search our yard for rocks and covered them in vinegar to observe what would happen.  I love watching my little scientists make their own experiments!  After letting the rocks sit in vinegar for several days we transferred the rocks and vinegar to a shallow pan and out it in the sun to allow the vinegar to evaporate.  

It's been fun to watch the crystals appear!

Share pictures of your rock collection on Instagram @pocketful_of_treasures or #pocketfuloftreasures