Handbook of Nature-Study · Lesson CCXVI · Topic 33: Crystals, minerals and rocks
216. Mica
Goal: Your child can split mica into thin sheets and describe how it bends, its luster and its uses.
You'll need
- A piece of mica (from a rock shop, or flakes found in granite or sand)
- A butter knife or a thumbnail
- A hand lens (magnifying glass)
- A nature notebook and a pencil (colored pencils if you have them)
What's in the book
The lesson has a leading thought, a short method, and four observations on splitting mica, how it looks and bends, its hardness and streak, and its uses.
The lesson, step by step
The leading thought
Mica is a crystal which flakes off in thin scales parallel with the base of the crystal. We rarely see a complete mica crystal but simply the thin plates which have split off.
Split it
Describe your piece of mica. Pull off a layer with the point of your knife. See if you can separate this layer into two layers or more.
A butter knife or a fingernail works well. How thin can you go?
Test it
Can you see through mica? Can you bend it? Does it break easily? What is the color of your specimen? What is its luster?
Can you scratch it with the thumb nail?
Uses
What are some of the uses of mica? How is it especially fitted for some uses?
Clue: it is clear, it bends, and it does not burn.
Find it in rocks
Look at granite or sparkly sand with the lens. The tiny flakes that glitter like mirrors are mica: light silvery ones, or black ones.
Nature notebook
Tape a thin sheet of mica into the notebook and write one sentence about it. Add a mica row to your mineral chart.
Answers to the book's problems
Mica splits into very thin sheets that you can see through; they bend and spring back. It has a glassy to pearly luster and is soft enough to scratch with a thumbnail. Because it is clear and does not burn, it was used for windows in stoves and lanterns; it is also used in electrical parts and to add sparkle to paints and makeup.
Worked out for this site from the scan. If a number in your copy differs, trust the book.