what are rocks made up of ?

Rocks are composed of different minerals and are classified into three major groups based on their formation process: igneous, sedimentary, and metamorphic rocks. The specific composition of a rock depends on the minerals present and the conditions under which the rock was formed.

To determine what a rock is made up of, you can follow these steps:

1. Observe the rock's appearance: Look at the color, texture, and size of the grains. This initial visual inspection can provide clues about the rock's composition.

2. Identify the rock type: Determine if the rock is igneous, sedimentary, or metamorphic. This can be done by considering its overall structure and formation history. Igneous rocks are formed from the cooling and solidification of molten material (magma or lava), sedimentary rocks are formed from the deposition and compaction of sediments, and metamorphic rocks are formed from the transformation of pre-existing rocks under high temperatures and pressures.

3. Observe the minerals present: Examine the rock closely to identify the minerals it contains. In some cases, the minerals may be visible to the naked eye, while in others, you may need a magnifying glass or microscope.

4. Conduct tests: To confirm the presence of specific minerals, you can perform simple tests like the scratch test (determining the hardness of a mineral using a mineral hardness scale), the acid test (reacting the mineral with acid to observe a fizzing reaction), or the streak test (rubbing the mineral on a porcelain plate to observe the color of the powder left behind). These tests can help identify minerals that are not apparent through visual inspection alone.

5. Consult reference materials: Utilize identification guides, mineralogy textbooks, or online resources to compare the observed characteristics of the rock and minerals with known examples.

By following these steps, you can determine the composition of a rock and gain a better understanding of its formation.