1. Crystalline Quartz  includes rose quartz, blue quartz, citrine, tiger's eye, amethyst, smoky quartz and milky quartz  SiO2-colors are created by impurities such as aluminum and iron, and by radioactivity  Arkansas and Brazil  Igneous and metamorphic rocks. pressure and temperature change crystalline structures  Pressure on it creates a small electrical charge, making it valuable for watches and clocks

2. Crystalline Quartz

3. Cryptocrystalline Quartz  Includes agate, jasper, onyx, and flint  SiO2-same as crystalline quartz but has microscopic crystals instead of visible crystals like the previous  Arkansas and Brazil  Igneous and metamorphic rocks. pressure and temperature change crystalline structures  Flint was often used for creating arrowheads by ancient cultures. Most cryptocrystalline quartz are transparent or translucent

4. Cryptocrystalline Quartz

5. Opal  Includes common opal, hyalite, geyserite, and tripolite  Noncrystalline silica containing water SiO2xnH2O  Western United States  low temperature deposits in hot springs and volcanic veins  some are hard enough to scratch glass (diatoms)

6. Opal

7. Diamonds  C (natural element) found as isometric crystals of crystalline masses  Australia, the Democratic Republic of the Congo, Botswana, Russia, and South Africa  Carbon (natural element) under extreme pressure and temperature changes  Made of the same stuff as graphite (pure carbon) but the crystalline structure of the atoms changes the physical property. Non- gem quality diamonds are used for industrial purposes

8. Diamonds

9. Aquamarine  Be3Al4Si6O18-beryllium ore derivative  Brazil, Pakistan, Russia, China, Nigeria, and New England  Igneous and metamorphic rocks. pressure and temperature change crystalline structures  semi-precious quartz, transparent

10. Aquamarine

11. Emerald  Be3Al4Si6O18-beryllium ore derivative  Columbia  Igneous and metamorphic rocks. pressure and temperature change crystalline structures  Precious quartz, transparent

12. Emerald

13. Jade  Amphiboles and pyroxenes  Al, Ca, Mn, and Fe silicates (Si compounds)  Myanmar (formerly Burma), Italy, Russia, Guatemala, and California. sometimes found in meteorites from outer space  igneous and altered rocks  Amphiboles and wedge-shaped and pyroxenes are squared. Green-tinted pyroxenes are precious

14. Jade