Lesson: Crystal Cavern

Discuss the article’s images and connect to students’ previous experiences.

• Share an image of a beautiful or interesting rock. Ask students if they have ever seen or found an impressive rock. 
• Ask: What did it look like? How big was it? Where was the rock? 
• Preview the article’s images of the giant crystals and the small geode. Ask: How do they compare with other rock formations you’ve seen?

Read and analyze an article about a giant geode.

• Read the article aloud as students follow along. In the section “Rare Rock,” focus on drawing and talking about the changes in the rock over time described in the first two paragraphs. When you read the “Gigantic Geode” sidebar, use the measurements to act out or demonstrate the rock’s size. 
• Read the directions for the 3-2-1 Reflection. Fill in one fact in the first section together. Then have students complete the skills sheet and discuss their responses in small groups before sharing with the class.

Develop a model showing how crystals form over time as mineral-rich water evaporates.

• Introduce the Crafting Crystals hands-on activity, discussing each step. If students will be doing the activity at home, emphasize that an adult must participate. Complete the activity and discuss the results.
• Tips for the activity: About nine teaspoons of salt per cup of water works well, but quantity depends on the size of the baking dish. The fewer additives (like iodine salts or noncaking agents) the salt has, the better the crystals will grow. However, iodized table salt will work. Regular paper will work, but the crystals are more visible on a dark background. If you leave the dish out until the water completely evaporates, students can observe and sketch the crystals.

Generate and communicate core ideas about rocks and minerals. 

• Create a T-chart with the left side labeled “Rocks” and the right side labeled “Minerals.” Tell students that together, you are going to list traits and examples of rocks and minerals. Add examples from the article, such as gypsum (mineral).
• Play the video “Rocks and Minerals.” Stop the video after rocks and minerals are defined and record each definition in the chart. Pause the video at least twice more to add examples and other information to the chart. Then ask students to describe in their own words how rocks and minerals are related. (Rocks are mostly made up of minerals.)

Check student understanding with a quick quiz and an open-ended activity.

• Have students complete the Quick Quiz before discussing the answers as a class. Then have them use the Learning Extension as a creative writing opportunity. Help students include vivid descriptions and scientific information. 

⇨ Learning Extension: Imagine you’re mineral collector Efrén Cuesta, discovering the Pulpí Geode in 1999. Write a story about entering the geode for the first time.