SHS_ Week 3 _Lesson 5 rocks and minerals.ppt
- 2. OBJECTIVES: At the end of the lesson, the learners will be able to: • demonstrate understanding about physical and chemical properties of minerals and will be able to identify certain minerals using specific tests; • identify some common rock-forming minerals; and • classify minerals based on chemical affinity.
- 3. WHAT IS A MINERAL? Mineral - naturally occurring, inorganic solid with orderly crystalline structure and a definite chemical composition. These are the basic building blocks of rocks.
- 4. CONSIDER WATER A MINERAL? HOW ABOUT SNOWFLAKE OR TUBE ICE?
- 5. Water is not a mineral since it is not solid and crystalline. Tube ice is not because it is not naturally occurring. Snow flake meets all requirements in defining a mineral.
- 6. WHAT ARE MINERALS? Minerals are the building blocks of rocks. Mineralogists use the criteria to determine whether a material is classified as a mineral or not.
- 7. CHARACTERISTICS OF MINERALS 1. naturally occurring- a product of Earth’s natural processes 2. inorganic- it must be product of Earth’s physical processes. 3. homogeneous solid- minerals should have definite volume and rigid shape 4. definite chemical composition—represented by a chemical formula 5. orderly crystalline structure- atoms of minerals are arranged in an orderly and repeating pattern
- 8. Mineral Name HALITE (TABLE SALT) Chemical Composition NaCl Luster non-metallic – vitreous; transparent to translucent Hardness soft (2-2.5) Color white Streak white Crystal Form / Habit cubic Cleavage perfect cubic Specific Gravity light (2.2) Other Properties salty taste; very soluble; produces reddish spark in flame
- 9. MINERAL PROPERTIES 1. Luster – it is the quality and intensity of reflected light exhibited by the mineral a. Metallic – generally opaque and exhibit a resplendent shine similar to a polished metal b. Non-metallic – vitreous (glassy), adamantine (brilliant/diamond- like),resinous, silky, pearly, dull(earthy), greasy, etc.
- 10. MINERAL PROPERTIES 2. Hardness – it is a measure of the resistance of a mineral (not specifically surface) to abrasion.
- 11. Hardness scale designed by German geologist/mineralogist Friedrich Mohs in 1812 (Mohs Scale of Hardness). The test compares the resistance of a mineral relative to the 10 reference minerals with known hardness. It is simply determining the hardness of a mineral by scratching them with common objects of known hardness
- 12. MOH’S SCALE OF HARDNESS
- 13. WHAT ARE THE PROS AND CONS IN USING THE MOHS SCALE OF HARDNESS? PROS CONS Easy to do the test The scale is qualitative and not quantitative Can be done anywhere, anytime as long as the place is not dark Cannot be used to test ccurate hardness of industrial materials Mohs scale is highly relevant for field geologists to roughly identify minerals using scratch kits Can be done without or few kits – handy
- 14. MINERAL PROPERTIES 3. Color and streak – Color maybe a unique identifying property of certain minerals (e.g. malachite –green, azurite – blue). There are also lots of minerals that share similar or the same color/s. In addition, some minerals can exhibit a range of colors. The mineral quartz for example, can be pink (rose quartz), purple (amethyst), orange (citrine), white (colorless quartz) etc.
- 15. MINERAL PROPERTIES 3. Color and streak –Streak on the other hand is the color of a mineral in powdered form. Note that the color of a mineral could be different from the streak. For example, pyrite (FeS2) exhibits golden color (hence the other term of pyrite which is Fool’s Gold) but has a black or dark gray streak.
- 16. MINERAL PROPERTIES 3.Color and streak – Streak is a better diagnostic property as compared to color. Streak is inherent to almost every mineral. Color maybe unreliable for identification as impurities within the minerals may give the minerals a different color.
- 17. The different colors and varieties of Quartz i s the result of impurities within the crystal structure. The color of some minerals can also be modified by weathering.
- 18. COLOR VS STREAK OF A HEMATITE (FE2O3). SOURCE: HTTP://WWW.INSTRUCTABLES.COM/ID/HOW-TO- IDENTIFY-A-MINERAL/STEP6/STREAK/ (8/30/2015)
- 19. MINERAL PROPERTIES 3.Color and streak – Streak is a better diagnostic property as compared to color. Streak is inherent to almost every mineral. Color maybe unreliable for identification as impurities within the minerals may give the minerals a different color.
- 20. MINERAL PROPERTIES 4. Crystal Form/Habit –The external shape of a crystal or groups of crystals is displayed / observed as these crystals grow in open spaces. The form reflects the supposedly internal structure (of atoms and ions) of the crystal (mineral). It is the natural shape of the mineral before the development of any cleavage or fracture. Examples include prismatic, tabular, bladed, platy, reniform and equant.
- 21. MINERAL PROPERTIES 4. Crystal Form/Habit – A mineral that do not have a crystal structure is described as amorphous. The crystal form also define the relative growth of the crystal in 3 dimension which are its length, width and height.
- 22. BLOCKY/CUBIC OR EQUANT (IT HAS EQUAL GROWTH RATE IN THREE DIMENSIONS).
- 23. BLADED HABIT (IT RESEMBLES A BLADE, WITH VARIED GROWTH RATES IN 3 DIMENSIONS
- 24. NEEDLE-LIKE HABIT (RAPID GROWTH OF CRYSTALS IN ONE DIMENSION WHILE SLOW IN OTHER DIMENSIONS
- 25. MINERAL PROPERTIES 5. Cleavage – It is the property of some minerals to break along parallel repetitive planes of weakness to form smooth, flat surfaces. These planes of weakness are inherent in the bonding of atoms that makes up the mineral. These planes of weakness are parallel to the atomic planes and appear to be repeating within the mineral.
- 26. MINERAL PROPERTIES 5. Cleavage – When minerals break evenly in more than one direction, cleavage is described by the number of cleavage directions and the angle(s) between planes (e.g. Cleavage in 2 directions at 90 degrees to each other).
- 27. one cleavage direction (biotite
- 28. cleavage in 2 directions at 90° (orthoclase).
- 29. 3 cleavage directions at 74°
- 30. MINERAL PROPERTIES 6. Fracture – Some minerals may not have cleavages but exhibit broken surfaces that are irregular and non-planar. Quartz for example has an inherent weakness in the crystal structure that is not planar. Examples of fracture are conchoidal, fibrous, hackly, and uneven among others.
- 31. MINERAL PROPERTIES 7. Specific Gravity – It is the ratio of the weight of a mineral to the weight of an equal volume of water. A bucket of silver (SG 10) would weigh 10 times more than a bucket of water (SG 1). It is a measure to express the density (mass per unit volume) of a mineral. The specific gravity of a mineral is numerically equal to density.
- 32. MINERAL PROPERTIES 8. Diaphaneity/amount of transparency - ability to allow light to pass through it. This is affected by chemical makeup of the mineral sample.
- 33. MINERAL PROPERTIES 9. Tenacity - describes the minerals reaction to stress. * Brittleness- a mineral turns into powder * Malleability a mineral can be flattened by pounding with a hammer. * Ductility- A mineral can be stretched into wire. *Flexible but inelastic-Minerals are bent but they remain in the new position. * Flexible and elastic- Minerals are bent, and they bring back to their original position.
- 34. MINERAL PROPERTIES 10. Sectility- ability of minerals to be sliced by a knife.
- 35. PROPERTIES 11. Others – There are certain unique properties of minerals that actually help in their identification(e.g. magnetism, odor, taste, tenacity, reaction to acid, etc.). Magnetite is strongly magnetic;sulfur has distinctive smell; halite is salty; calcite fizzes with acid as with dolomite but in powdered form.
- 36. Can you think of a way to group minerals together?
- 37. Physical properties are useful for mineral identification, some minerals however may exhibit wider range of properties to include chemical compositions.
- 39. 1. Silicates – minerals containing 2 of the most abundant elements in the Earth’s crust, namely, silicon and oxygen. When linked together, these two elements form the silicon oxygen tetrahedron – the fundamental building block of silicate minerals. Over 90% of the rock-forming minerals belong to this group. Aside from Si (46.6 % by wt.) and O (27.7%), the other most common elements that make the earth’s crust are Al (8.1), Fe (5.0), Ca (3.6), Mg (3.1), Na (2.8) and K 2.6).
- 40. 2. Oxides – minerals containing Oxygen anion (O2-) combined with one or more metal ions 3. Sulfates – minerals containing Sulfur and Oxygen anion (SO4)- combined with other ions 4. Sulfides – minerals containing sulfur anion (S2)- combined with one or more ions. Some sulfides are sources of economically important metals such as copper, lead and zinc.
- 41. 5. Carbonates – minerals containing the carbonate anion (CO3)2- combined with other elements 6. Native Elements – minerals that form as individual elements. a. Metals and Inter-metals – minerals with high thermal and electrical conductivity, typically with metallic luster, low hardness (gold, lead)b.
- 42. b. Semi-metals – minerals that are more fragile than metals and have lower conductivity (arsenic,bismuth)c. c. Nonmetals – nonconductive (sulfur, diamond) 7. Halides – minerals containing halogen elements combined with one or more elements