1. Toothbrushes and toothpastes usually consist of mica (it provides sparkles), limestone (it rubs away plaque), and plastic (it forms the handle and bristles). Which of these ingredients is a...

1. Toothbrushes and toothpastes usually consist of mica (it provides sparkles), limestone (it rubs away plaque), and plastic (it forms the handle and bristles). Which of these ingredients is a mineral? Which is a rock? Which is neither rock nor mineral?

2. Why are intrusive igneous rocks coarse grained? Why are extrusive igneous rocks fine grained?