... Topic 1: Page 47 Earth Textbook Rock- Forming Minerals common minerals that make up the Earth’s crust * over 2000 minerals known * most are silicates (Si + O + metals) * ... Cleavage minerals split along flat surfaces direction – micas, gypsum, talc directions – feldspars, hornblende directions – galena, halite, calcite Topic 3: Page 49 Earth Textbook Fracture minerals ... rough surface Topic 3: Page 49-50 Earth Textbook Hardness minerals resistance to being scratched *Mohs’ Hardness Scale – page 50 in text minerals ranked on a scale of to 10 •need fingernail, copper,...