1. PRECIOUS STONES GRADE: 6° TEACHER: LILIANA TOLEDO M OA: Identificar léxico de la unidad

2. DIFFERENT PRECIOUS AND SEMIPRECIOUS STONES

3. PRECIOUS STONES OR GEMS THE FOUR GEMS CONSIDERED AS PRECIOUS STONES OR GEMS ARE: EMERALD, RUBY, BLUE SAPPHIRE AND DIAMOND

4. SEMIPRECIOUS GEMS Agate is a form of chalcedony quartz that forms in concentric layers in a remarkable variety of colors and textures. Alexandrite is one of the rarest of all colored gemstones and is famed for its color change from green in daylight to red under incandescent light. AGATE ALEXANDRITE

5. SEMIPRECIOUS GEMS: AMETHYST Amethyst is the most precious gemstone within the quartz group. Amethyst ranges in color from pale lilac to deep reddish purple.

6. SEMIPRECIOUS GEMS: AQUAMARINE Aquamarine is best known for its breathtaking range of blue colors. Aquamarine is colored by trace amounts of iron.

7. SEMIPRECIOUS GEMS: LAPIS LAZULI Lapis lazuli is a rock whose most important mineral component is lazurite. Most lapis lazuli also contains calcite (white), sodalite (blue), and priste (metallic yellow). We find it in Russia, northeast of Afghanistan and in the Andes Mountains in Chile.

8. SEMIPRECIOUS GEMS: ONIX Onyx is the black form of chalcedony Onyx is a banded variety of chalcedony The colors of its bands range from white to almost every color

9. SEMIPRECIOUS GEMS: OPAL More than any other gem, each opal is unique. Opals are also the most delicate gems commonly worn.

10. SEMIPRECIOUS GEMS: QUARTZ There are many different varieties of quartz, several of which are semi- precious gemstones Especially in Europe and the Middle East.

11. SEMIPRECIOUS GEMS: ROSE QUARTZ Rose Quartz is a type of quartz which exhibits a pale pink to rose red color. The color is usally considered to the amounts of titanium, iron, or manganese

12. SEMIPRECIOUS GEMS: TOPAZ Topaz is an important gem due to its hardness. Topaz comes in many colors but the blue topaz is especially popular.

13. SEMIPRECIOUS GEMS: ZIRCON Zircon has great brilliance and intensive fire. Zircon is found in most igneous rocks and some metamorphic rocks as small crystals or grains

14. SEMIPRECIOUS GEMS: TURQUOISE Turquoise, the blue cousin to lapis lazuli, has been known and valued for thousands of years. The early mines in Sinai, Egypt, were already worked out in 2000 B.C.

15. SEMIPRECIOUS GEMS:AMBER Amber, the fossilized, hardened resin of the pine tree, is one of the few gemstones of organic origin. Most amber is found in the Baltic, where it formed about 50 million years ago.

16. SEMIPRECIOUS GEMS: CORAL Precious coral is a species of coral that grows in rocky seabottoms. Coral exhibits a range of warm reddish pink colors ranging from salmon pink to deep red. Gemstones of organic origin. The most valuable coral variety is found in the Mediterranean, the Red Sea and in coastal Japan.

17. IVORY Ivory originally referred to the material of the elephant's tusk. Today ivory also comes from the teeth of hippopotamus, walrus, wild boar and other mammals. Like bones, ivory consists mainly of calcium phosphate. Ivory is of organic origin.

18. SEMIPRECIOUS GEMS: PEARLS Pearls are products of bivalve mollusks (mainly oysters and mussels). They are built up of nacre, which is mainly calcium carbonate. They’re of organic origin