Red rocks are often evidence of iron deposits
Identifying rocks and understanding the geological history of an area can add a whole new layer (no pun intended) to your understanding of the area in which you live or areas to which you travel. Every rock is evidence of complex geological processes stretching back billions of years that can, nonetheless, be understood through looking at superficial rocks and mineral deposits. Taking a specific kind of rock, in this case red rocks, you can use the steps in a rock key to examine the rocks in question, classify the rocks and better understand the geological processes that act on the area.
Instructions
1. Look at the surface of the rock to see if it is coarse-grained, ending in jagged ends and having a somewhat boxy appearance, or smooth with a uniform consistency and rounded shape. Try throwing the rock against the ground to see if it breaks along even lines, likely for smooth rocks, or into the jagged ends of a coarse rock.
Red marble and quartzite, for instance, are coarse rocks, but red slate will break along the straight lines of its layers.
2. Examine the surface of the rock to look for crystal grains and layering. Crystal grains will reflect light back off the surface of the rock and will appear to shine, while layers will simply be different shades of color compressed in layers along the surface of the rock. A rock can have crystalline grains, layers, both or neither.
3. Notice the shape of crystal grains and layers. Layering and crystal grains are usually in straight lines or in curved ribbon shapes, each serving to identify the types of minerals present in a rock from the way in which they settle on the rock.
Red sandstone, for example, usually has rounded grains, while shale tends to have fine, straight grains.
4. Test the rock against a piece of glass to see if it will produce a scratch. Gently run a corner of the rock over a piece of glass about half an inch and look at the glass to see if the friction caused a mark. This step will determine the hardness of your rock.
As an example, red marble is a very soft rock that will not scratch glass, while rhyolite is very hard, formed from cooled magma with large amounts of quartz, and will scratch glass easily.
5. Run the tip of steel nail across the surface of the rock. Touch the tip of the nail with your finger to see if the nail merely scratched the surface of the rock or produced sand from friction with the stone. This step will help you identify mineral components in your rock.
6. Compile all of the information gathered from the previous tests and compare it against the characteristics listed in a rock key to identify the rocks in question.
Tags: surface rock, crystal grains, geological processes, grains layers, jagged ends
