Identifying rock samples is sometimes overwhelming to young students. Since there are three classes of rocks, each which have many different types, it can be very confusing when you start to explain the differences between each, especially because some look so much alike! If possible, teach the students about mineral identification before you move on to rocks, after all, rocks are simply a combination of one or more minerals.
Tip #1: Give the students physical samples that they can examine and touch. A hands-on method improves a child’s understanding of rock color and texture. A picture or poster is not as effective as teaching with hands-on learning because rock texture differences can be very subtle and not easily determined in photographs. Also, allow the students to use a hand lens to magnify the rock and made details easier to observe.
Tip #2: Explain the three basic types of rocks to the students. If you have samples, show samples to the students making sure that they samples look very different from each other. Elementary students do not need to know the details of each type of rock, just the general look and feel of the different types.
- Sedimentary Rocks = rocks formed in lakes, rivers, oceans and deserts,
- Igneous Rocks = rocks from either underground or above ground from volcanoes,
- Metamorphic Rocks = rocks that were once a different type of rock but were buried deep below the Earth’s surface and were changed from high temperatures and high pressures.
Tip #3: Use flow charts that are easy to read with limited arrow options so the choices are obvious. Mini Me Geology has free, downloadable flow charts that you can use for identifying common rocks. The flow charts work by sorting the rocks with texture, color and special features going from left to right across the chart. These charts correspond to our deluxe kits; however, as long as you have several samples from the chart you do not need the entire kit. Click the links to download the free identification flow charts for sedimentary rocks, igneous rocks and metamorphic rocks.
These basic charts are perfect for elementary students because there are only three steps to finding the name of the sample. The texture identifies the rocks grain size. A hand lens is useful during this step. The Dig Into Geology section of our website has articles that will help your students properly focus the hand lens and perform a “fizz” test for identifying limestone. You can read these articles here.
Tip #4: Limit samples to two to three rocks of each type. For example, granite and obsidian are all igneous rocks that look very different. Granite shows students how volcanic magma cools slowly underground and forms grains in the rock that are easy to see. Obsidian forms outside of the volcano and cools so fast that you cannot see any grains. Following are suggested rocks for your lessons.
- Sedimentary Rocks – coquina (made of shells and fizzes with an acid), limestone (fine-grained and fizzes with an acid), and sandstone (coarse grained and will not fizz with an acid),
- Igneous Rocks – obsidian (forms outside and looks like glass), volcanic breccia (has two grain sizes from the erupting volcano), and granite (forms inside and has easy to see grains),
- Metamorphic Rocks – gneiss (was granite and can see grains in layers), marble (was limestone and fizzes), and quartzite (was sandstone and does not fizz).
Tip #5: Allow your students to work alone before walking them through the solution. Identifying rock samples helps develop logical thinking skills that transfer from science to other subjects as the children progress in school. Before they begin, explain how to use each flow chart. As the kids determine each property, they can physically move the rock sample from one block to the next until they reach the name of the rock.
If you need help choosing sedimentary, igneous or metamorphic rock samples for your students or explaining the properties of each, please contact us at email@example.com and we will help you have a successful rock lesson.