1. MINERALS

2. What is a mineral ?  Naturally occurring  Inorganic  Solid  Crystal shape  Definite chemical composition

3. Naturally occurring Means…they are not made by humans (they are formed by the earth).

4. Inorganic Means………….. they have never been alive and are not made of plants or animals.

5. Solid Means……….they are solids, not liquids (like water), or gases (like the air around you)

6. Means…………they have an ordered atomic arrangement. The chemical elements that make up each mineral are arranged in a particular way - this is why minerals “grow” as crystals. Crystal shape

7. Definite chemical composition Means……..each mineral is a pure substance. Minerals can be elements or compounds. Sulfur (S) - element Halite (NaCl) - compound

8. QUIZ As we go through the next few slides, decide (in your head) whether each substance is a mineral or not. Hematite Charcoal Mineral Not

9. Mineral or Not ? Think about it. Does anybody make quartz? Where do you think it is found? Does it have a crystal structure? Quartz

10. Mineral Quartz is a mineral. You have probably seen a quartz crystal in a museum or rock shop. It is a naturally occurring, inorganic, solid, with a definite chemical composition, and an ordered atomic arrangement!!!

11. Mineral or Not ? Think about it. Who makes plastic? It may look pretty inorganic, but do you know what plastic is made from? Plastic

12. Not Plastic is not a mineral. Plastic is not mineral. It is a solid, and it has a definite chemical composition. However its atoms do not have a crystal shape. Plastic is made from oil (an organic material) by humans - plastic is not a naturally occurring substance. Plastic is not a mineral.

13. Mineral or Not ? Think about it. Can you make gold? You can make gold jewelry, but where do you find gold nuggets? Does it have a crystal shape? Gold

14. Mineral Gold is a mineral. You may think of it as a metal, but native gold is a mineral too. It is a naturally occurring, inorganic, solid, with a definite chemical composition, and an ordered atomic arrangement (crystal shape) !!! Gold crystal 

15. Mineral or Not ? Granite Think about it. What do you think it is made of? It has lots of different types of crystals, and they are all jumbled up together. Does it occur naturally?

16. Not Granite is not a mineral. Granite is a rock and not a mineral, but rocks are made of minerals. The minerals in granite - quartz, mica and feldspars - are all jumbled together. Some granites have more quartz than others; granite does not have a fixed chemical composition. Remember, rocks are made up of minerals, but that doesn't mean that rocks ARE minerals.

17. Tests for Identifying Minerals It is very difficult to tell one mineral from another just by looking at it. We will use several tests and resources in order to identify a mineral. Are the two minerals on this page the same mineral or different minerals?

18. Cinnabar Beryl DIFFERENT

19. Try this one. Are these the same mineral or different minerals?

20. Gypsum SAMESAME

21. Tests for Identifying Minerals 1.Color 2.Luster 3.Streak 4.Hardness 5.Density 6.Crystal shape 7.Cleavage and/or Fracture (Breakage) 8.Special Properties

22. 1. Color Most minerals have a variety of colors. All of the samples above are quartz.

23. Color can also be unreliable because it can change. Some minerals have metals in them which can oxidize or rust when exposed to the weather. Chalcopyrite (gold color) with quartz (colorless) Chalcopyrite after being exposed to the weather.

24. Tarnished silver Gold is one of the only metals that will not oxidize (rust or tarnish) when exposed to the elements - which is why it is a good choice for jewelry. Silver

25. white colorless beige dirty-white red purple mauve pink salmon pink blue bluish turquoise green silvery -yellow gray grayish-black silver black golden gold-colored yellow bronze brown copper-colored silvery-white with black specks Be very specific when recording colors !

26. How would you describe the color of these minerals ?

27. 2. LUSTER Luster describes the way a mineral reflects light. There are two types of luster: 1. Metallic 2. Nonmetallic

28. Metallic Luster Metallic luster is shiny like a metal. (don’t forget that minerals with metals in them can tarnish or rust) Copper Gold Magnetite Graphite Galena Pyrite Magnetite Silver Hematite

29. Nonmetallic Luster Luster that does not look like a metal. With nonmetallic luster, you need to specify the type. Malachite (waxy) Beryl (aquamarine) (glassy or vitreous) Kaolinite (earthy) Muscovite mica (pearly) Diamond  (greasy) (brilliant) 

30. Luster:Description: dull / earthyvery dull ; looks like earth waxylooks like a chunk of wax greasy / oilyhas a oily, reflective surface pearlylike a pearl, play of colors, light silky / velvetylooks like it has a soft, smooth surface resinouslooks like dried glue or gum, usually yellow-brown glassy / vitreouslooks like glass adamantinehigh luster, almost brilliant brilliantlooks like a gem Words that describe non-metallic lusters

31. Check yourself. What type of luster is shown ? Metallic or Nonmetallic ?????

32. Biotite mica ( nonmetallic - pearly) Goethite (nonmetallic -earthy) Chalcopyrite (metallic) Quartz (nonmetallic - glassy or vitreous)

33. 3. Streak Streak is the color of the powder left by a mineral when it is rubbed against a hard, rough surface (streak plate). Good test, except when: Mineral is harder than 7 (mineral is harder than streak plate) Mineral is a light color (when using a white streak plate)

34. What color would you expect the streak to be for these two elements ?

35. Metallic hematite Earthy hematite Both of these minerals are hematite, so they will produce, basically, the same color streak.

36. 4. Hardness Hardness is the ability of a mineral to resist being scratched. Two Hardness Scales: 1. Mohs Hardness Scale 2. Field Hardness Scale Very useful test, but often incorrectly performed

37. Mohs Hardness Scale Scale goes from 1 - 10 Different minerals represent different hardnesses Field Hardness Scale o Scale goes from 1 - 7 o Different instruments are used to measure hardness

38. Mohs Hardness Scale  Scale goes from 1 - 10  Different minerals represent different hardnesses 1 - Talc 2 - Gypsum 3 - Calcite 4 - Fluorite 5 - Apatite 6 - Feldspar 7 - Quartz 8 - Topaz 9 - Corundum 10- Diamond

39. Field Hardness Scale Hardness Common Test 1 ……………………… Easily scratched with fingernail (2.2) 2 ……………………… Scratched by fingernail (2.2) 3 ……………………… Scratched by a copper penny (3.5) 4 ……………………… Scratched easily by a pocket knife (5.2) (or a common nail), but will not scratch glass 5 ……………………… Difficult to scratch with a knife (5.2) (or a common nail); barely scratches glass (5.5) 6 ……………………… Easily scratches glass (5.5) 7 ……………………… Easily scratches glass (5.5)

40.  Each mineral can scratch the minerals with lower hardness ratings.  Each mineral can scratch itself.  Don’t press hard, normal scratching should do.  Weathered surfaces are softer.  Corners or edges of crystals are softer.  Small pieces seem softer than large pieces.  When you scratch, take a close look at the scratch line- which often looks white. Is it really a scratch, or is it a powder line made from the tool you used because it was softer than the item you were trying to scratch. Helpful hints for conducting the hardness test:

41. 5. Specific Gravity (Density) This characteristic relates to the mineral’s density. If the mineral is heavy for its size, then it has a high specific gravity. Water displacement is useful in determining specific gravity. Specific gravity is only helpful if the sample is pure.

42. 6. Crystal Shape Crystal shape is the repeating atomic pattern within the mineral. Each mineral has a certain crystal pattern when the mineral is forming. There are 6 crystal forms: 1.Cubic 2.Hexagonal 3.Orthorhombic 4.Monoclinic 5.Tetragonal 6.Triclinic You will seldomly see minerals in their crystal form in class.

43. Cubic Orthorhombic Tetragonal Tetragonal crystals are shaped like cubic crystals but are longer in one direction making shapes like double pyramids and prisms. Cubic crystals are not always cube shaped! There are many that are shaped like octahedrons (eight faces), and some that are shaped like dodecahedrons (10 faces). Orthorhombic crystals are often shaped like rhombic prisms or dipyramids (two pyramids stuck together). They often look a bit like tetragonal crystals except that they are not square in cross section (when you look at the crystal on end).

44. Monoclinic Hexagonal Triclinic Hexagonal crystals often look like six-sided prisms. When you look at the crystal on end, it looks like a hexagon shape in cross section. Monoclinic crystals look like tetragonal crystals that have been skewed. They often form prism shapes and double pyramids. Triclinic crystals are sometimes very strange shapes! They are usually not symmetrical from one side to the other.

45. 7. Breakage (Cleavage and Fracture) Cleavage is when a mineral breaks on a smooth, definite surface. Fracture is when a mineral breaks unevenly or with a rough break. You will not actually break the minerals but look at how they have broken in the past.

46. Cleavage Words associated with Cleavage: perfectfibrous90  booksplatesoctahedraldodecahedral cubicbasalhexagonalprismatic (prism) two planesmonoclinicsheetsrhombohedral ___ directions (ex. 2 directions, 4 directions)

47. Fracture Words associated with fracture: Conchodial Uneven Imperfect Irregular Fracture Hackly No cleavage

48. 8. Special Properties Some minerals have special properties. For example: Magnetism Fluorescent Unusual taste or smell Effervesces (fizzes) in acids

49. Magnetism MAGNETISM Some minerals containing iron can be magnetic. They act just like the refrigerator magnets you find at home. Magnetite (iron oxide) is the only common mineral that is strongly magnetic. The simplest test for magnetism is to use a compass. A magnetic material will move the needle away from its usual position, pointing northwards. In the picture on the right, paperclips are attracted to the mineral magnetite.

50. Taste This will quickly identify the mineral halite (salt). If you are new to this process you must use this one with caution, as you never know what the unknown may be. If you were to taste the sample (especially in a class environment), you should realize that it has been handled by and probably tasted by hundreds of others. YUCK !!!

51. Reaction to Acid The carbonate minerals react with dilute hydrochloric acid (HCl) by fizzing, producing bubbles of carbon dioxide gas (the same type of harmless gas bubbles that are found in carbonated beverages). Calcite fizzes readily in hydrochloric acid. Dolomite will fizz if it is first scratched and powdered. You may use a nail or steel needle probe to scratch the specimen to try this test. CaCO 3 + 2HCl =====> CaCl 2 + H 2 O + CO 2 (calcite) (hydrochloric acid) (calcium chloride) (water) (carbon dioxide)

52. This is also known as double refraction. Birefringent minerals split the light into two different rays which gives the illusion of double vision as in this calcite. Birefringence Optical Calcite

53. Some minerals display what is called the phenomenon of photoluminescence. This basically means that they "glow" when exposed to UV light (black light). The mineral fluorite is often strongly fluorescent. Fluorescence Willemite Benitoite

54. Special Properties of Ulexite This specimen of Ulexite that has been cut top and bottom with a diamond saw. This view shows the silky texture produced by the fine, acicular crystal growth. When viewed parallel to the fibers, Ulexite transmits light in a similar fashion to fiber optics. It is this property that has given rise to it nickname of "TV" stone. Ulexite NaCaB 5 O 9 - 8H 2 O (Hydrated sodium calcium borate)

55. Starter In your mineral notes, give the color and luster for each of the minerals below. topazgalena

56. topazgalena Burnt orange Nonmetallic - glassy (vitreous) White-silver Metallic

57. Practice Mineral Identification Use a mineral chart to identify these minerals. 1. This mineral has a hardness of about 6, and has a metallic luster. It is dark gray to black in color and has cleavage. It has a black streak. What mineral is it? 2. This mineral looks very glassy. It could scratch glass fairly easily. It is a greenish color with a white streak. I don’t think it has cleavage. What mineral is it? 3. I have a huge piece of this mineral. I cannot scratch it with my fingernail, but I think that I scratched it with a penny. The nail definitely scratched it. It has a glassy, clear look, and seems to have a lot of flat surfaces. I don’t think it left a streak. What mineral is it?