- Formation of minerals from magma and lava
- Formation of minerals from solutions
- Describe how melted rock produces minerals.
- Explain how minerals form from solutions.
lava: Molten rock that has reached Earth’s surface.
magma: Molten rock deep inside Earth.
rock: Mixture of minerals.
Introducing the Lesson
Ask students to recall from Lesson 3.1 the criteria that must be met in order for a substance to be classified as a mineral. (It must be a solid, be inorganic, have a definite chemical composition, have a crystal structure, and form by natural processes.) Tell students they will learn in this lesson about some of the natural processes that lead to the formation of mineral crystals.
Use the demonstration at the URL below to show students the effects of cooling rate on crystal size. In the demonstration, you will simulate the growth of mineral crystals using some common materials (e.g., mothballs, crayons) because growing actual mineral crystals—for example, from a supersaturated solution of salt—takes too long for a classroom demonstration.
Have students grow their own mineral crystals from a solution. The activity at the URL below shows them how. This is an activity they can do at home or in the classroom over multiple days. Make sure that students make daily observations of their crystals and record their observations in their science notebook.
Have students make a KWL chart before reading the lesson and fill in the first two columns (Know, Want to Know) with regard to how minerals form. After they finish reading the lesson, have them fill in the last column (Learned). Did they learn everything they wanted to know? If not, provide the missing information if possible.
Tell the class that geodes have been called the “tootsie roll pops of the geology world” (http://www.rocksandminerals4u.com/geodes.html). Call on one or more volunteers to learn more about geodes and then explain to the class why geodes have been compared to tootsie roll pops. The URL below is a good starting point for learning more about geodes.
In the activity at the URL below, students will observe four different minerals growing under magnification. They will draw what they observe and then answer a series of questions to analyze their observations and how they relate to the formation of mineral crystals in nature.
Some people hold the misconception that diamonds form from coal. Tell students that although both diamonds and coal consist only or mainly of carbon, diamonds rarely, if ever, form from coal. Almost all diamonds form in igneous rocks in the mantle and make their way to the surface by volcanic eruptions. Discuss the following evidence with students so they will see why the misconception is false. (You can learn more at http://geology.com/articles/diamonds-from-coal/).
- Most diamonds that have been dated are older than the first land plants. Because coal formed from land plants, it must be younger than most diamonds. Therefore, most diamonds could not have formed from coal.
- Coal seams are sedimentary rocks that usually form more-or-less horizontal rock units. Diamonds, in contrast, form in vertical igneous rock units, called pipes.
Reinforce and Review
Copy and distribute the lesson worksheets in the CK-12 Earth Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.
Lesson Review Questions
Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition;.
Check students’ mastery of the lesson with Lesson 3.3 Quiz in CK-12 Earth Science for Middle School Quizzes and Tests.
Points to Consider
When most minerals form, they combine with other minerals to form rocks. How can these minerals be used?
The same mineral can be formed by different processes. How can the way a mineral forms affect how the mineral is used?