Week 6: Hunting and Describing Rocks
A Rock is a Rock is a Rock, Isn’t it?
We all know rocks are hard and found in the ground, but what else can we say about them? Rocks are very diverse, made of different minerals, forming different shapes, and found in different places. Here in the Finger Lakes, where our land was once the bottom of a deep ocean, most of our rocks are made from sand and silt that have been pressed, into rocks. This week, we’ll look for rocks in our backyards, learn how to explore their qualities, and then use them to make a rock garden!
Backyard Activity: Find and Describe Rocks
Rock scientists, known as geologists and more specifically, petrologists, have many very specific ways to describe the rocks they find. This week, go out into your backard and find a bunch of rocks! Then use the qualities of rocks below to draw and describe them in your field journal. When you’re done, we’ll use those rocks you found to make a rock garden!
Ways to Describe Rocks
Luster
The word luster comes from the Latin word lux, which means light. Luster describes the way light shines off a rock. For example, a rock has metallic luster when it reminds you of shiny metal. A rock has greasy luster when it reminds you of what your skin looks like when you put lotion on it. A rock has dull luster when it doesn’t shine very much in the light and a rock has resinous luster when it reminds you of plastic or chewing gum. If you want to learn lots more about luster, check here!
(Image by James St. John)
Hardness
Hardness describes how easily a rock can be scratched by other minerals. One of the softest minerals is Talc, which is almost powdery and can be easily scratched by other minerals. The hardest mineral is diamond, which cannot be scratched by other minerals. When you go rock hunting, bring a penny and a magnifying glass along. You can use the penny to try to scratch the rock. Then examine how deep the scratch is by looking at it with your magnifying glass. By comparing the depth of the penny scratches, you’ll be able to compare the hardness of the rocks you collect. Learn about the Mohs scale of hardness here.
(Image by Ra’ike)
Color
Sometimes it’s easy to describe a rock by one color: gray, white, orange. But sometimes a rock will be more than one color or have a pattern of different colors on it. In those cases we might use words like striped, spotted, streaked, swirled. When you describe the color of the rocks you find, make sure to be specific! For a list of lots of words to use to describe rocks, check here.
(Image by WildHeartPioneer)
Texture
Texture is the way something feels under your fingertips. We usually use words like rough, smooth, and slippery to describe texture. Petrologists, however, use very unusual and specific words for the texture of rocks. Here are a few basic ones that we can use when exploring rocks in our backyard. Crystalline means that when we look at the rock up close, we see small crystals or chunks of different sizes that compose the rock. Granular means that when you look at the rock up close, you see small grains of even size. If you want to learn a lot more about rock texture, watch this video.
Craft: Rock Garden
In your packets, you’ll find a black container, potting soil, and a small succulent plant. Here are the steps to make your rock garden:
1. Pour the potting soil into the black container.
2. Plant your seedling in the soil.
3. Cover the soil with rocks you found. If you have lots of small rocks, you can mix them into the soil before you plant the seedling.
4. Water just a little bit around the plant.
Succulents are like cactuses – they don’t need much water. Water a little bit only when the soil feels completely dry. Learn more about this project here.
Craft: Hag Rock Necklace
Our librarian Heather’s mom gave us the gift of a big bag of rocks all with small holes in them. These special rocks are also known as hag stones, and can be formed by water erosion or by a small creature called a mollusk. You’ll find one rock and a length of string in your packet. Thread the rock onto the cord, tie a knot, and you’ll have a necklace!
