Mistery Mineral Match

We have started already studying about minerals in the science class. Yesterday we went to the laboratory to perform some tests that geologists use to discover the minerals present in rock samples.
All rocks are composed of minerals. The combination of minerals determines the rock type. Rocks with high concentrations of valuable minerals are mined for human use. Minerals have characteristic properties that can be used by geologists to help identify them, such as color, hardness, or shape.
Geologists are the scientists who prospect, or explore, for minerals found inside the Earth. These scientists carefully make observations and record data to help them answer questions about the resources contained inside the Earth's crust. Through careful study, geologist have discovered that although there are over 3000 different minerals, 90% of the Earth's crust is made of only 20 of them.
The minerals that make them up are important to us because we derive, or take what we need from them. For example, lead can be derived from the mineral galena. People use lead to make batteries, ammunition and antiknock additives for gasoline. Mining minerals is expensive, but we have come to depend on minerals in manufacturing the products we use every day. Minerals that are rare or especially beautiful are called gemstones. Most gemstones are colorful crystals of common minerals. Graphite, or pencil "lead", changes into diamond under enormous pressure.