GEO 111 Cuyamaca College Rock Forming Minerals Geology Lab
Overview:We will be looking at minerals - the basic building blocks of rocks! Instructions:You will need to open the Mineral Database to help with this lab.The Mineral Properties Information will also help explain each of the different mineral properties.Open Lab 3: Minerals.
The lab is pasted below as well.If you purchased the lab manual, turn to page 18.Upload the completed handwritten document.If you're not sure how to do this, here's a tutorial.Physical Geology 111 LaboratoryMINERALS I – Properties, Classification, and IdentificationINTRODUCTION: The purpose of this lab is to learn the characteristics of minerals, and to identify minerals in hand samples from their physical properties. You will become familiar with a number of common rock-forming minerals and several other minerals that are less common, but are important because they are the principal sources of economically important materials (such as iron and copper). The objective of this lab is for the student to be able to identify major rock-forming minerals hand specimens by determining their physical properties.I. MINERAL DEFINEDA mineral is defined by five attributes; a substance must possess these five attributes to be labeled a mineral. Directions: List the five attributes for a mineral.Does water or ice meet this definition of a mineral? Justify your answer.Water - Yes or No? Why? Ice - Yes or No? Why? II. HARDNESSSome minerals are harder than others. Each mineral has a specific hardness (or at least a restricted range). You can test this for yourself because harder minerals will scratch softer Choose two mineral samples and try it yourself. A mineral's hardness sometimes determines its usefulness as an economic material. Cutting, grinding, and polishing tools typically require abrasives with a specific hardness, depending on the material being worked on. Hard minerals, such as garnet, corundum, and diamond, are used as abrasives for working with hard stone or metals. Some hard minerals are also attractive as gemstones, due in part to their resistance to scratching. Soft minerals such as calcite are used as mild abrasives and polishes where the working material is more delicate.Question: Why would a soft mineral be a poor choice for a gem, even if it were very attractive?Soft minerals are sometimes used as mild abrasives if the working material is also soft. Question: Can you think of a mineral that you probably use every day as a mild abrasive/polish?Questions: Why does it have to be soft? What would happen if it were replaced with a hard abrasive?A mineral hardness scale, called MOHS HARDNESS SCALE, uses 10 specific minerals - each with a unique and different hardness (1 to 10) - for comparison with other The 10 minerals are arranged in order of hardness and numbered from one to ten on the scale of hardness. Directions: List the 10 Mohs Hardness minerals below.Soft minerals: 1) 2) 3) 4) 5) Hard minerals: 6) 7) 8) 9) 10) Question: Guess why the #10 hardness mineral is missing from your mineralIdentifying Minerals by Hardness: When geologists need to identify minerals in the field they frequently carry a mineral hardness kit to test field samples for mineral hardness. However, most of us do not walk around with a hardness kit for checking mineral hardness, so it is difficult to make a hardness comparison of minerals when out in the field. So, we can use more common items in place of the Mohs minerals.What is hardness for these common items below? Streak plate = ______ Glass plate = ______ Knife blade = ______ Iron (carpentry) nail = ______ Copper penny = ______ Fingernail = ______Note that specimens equal to or harder than feldspar (H = 6) are considered "HARD". A “Hard” mineral will scratch glass (H = 5.5). Specimens softer than Flourite (H = 4) are considered "SOFT".If you're in the field, which of the above test item(s) appears to the BEST hardness-testing tool for identifying the "HARD" minerals from the softer minerals?Answer .Which Mohs minerals is the hardest that you can scratch with your thumbnail?Which Mohs minerals is the hardest that you can scratch with a carpenters nail?Which Mohs minerals is the softest mineral that will scratch a glass plate?III. LUSTERThe luster of a material refers to the way it reflects light. Is it shiny like glass, metallic like metal, waxy like a candle, pearly like pearl, dull, etc? The various mineral lusters are listed and described in the MINERAL DATABASE. Each mineral has a characteristic luster. A single mineral type may have several lusters, depending on the sample. The most preliminary criterion for identifying a mineral is whether a mineral has a metallic versus nonmetallic Note that many metal-bearing ores have a metallic luster, whereas, all the silicate and carbonate minerals have a non- metallic luster.Directions: Classify mineral samples in the box collection according to their luster: List the sample numbers in the correct category.Metallic Luster Samples #’s: Nonmetallic Luster Sample #’s : IV. COLOR and CLARITYThe color of a mineral can be helpful but also misleading when determining its identity. Quite a few minerals have a variety ofThere are more than one variety of quartz in your mineral box. Why does this mineral have multiple colors?V. CLEAVAGESome minerals break along smooth, flat, parallel surfaces called CLEAVAGE PLANES. These smooth, flat, shiny surfaces are planes of weakness in the mineral crystal. When a mineral "cleaves" or breaks into an easily recognized shape it will help us to recognize the mineral. Cleavage of a mineral is described in terms of, the number of uniquely oriented cleavage planes, the quality (perfect, good, poor), and the angles between the cleavage planes. For example the cleavage of the mica minerals, like biotite and muscovite, have one single perfect cleavage plane, as you can cleave the mineral into thin flat “plates” or “sheets”. Check for mineral cleavage by turning the sample back and forth, as you look for patches of bright reflected light emitted from mineral cleavage surfaces. If cleavage is present, then determine how many co-planar sets of cleavage are present. Note that some minerals completely lackDirections: Carefully examine the following mineral samples. 1) Determine each listed mineral’s unique cleavage. 2) Check your determination with the cleavage listed for that mineral in the MINERAL DATABASE. 3) Match each mineral(s) below to their correct type of cleavage character (use the Capital Letter assigned to cleavage type). Note: Two groups below have same type of cleavage.Mineral Type of Cleavage Feldspar and Pyroxene A = no cleavage/ only fractureMagnetite and Pyrite B = 1 direction - perfectGalena and Halite C = 2 directions @ 90 - good;Calcite and Dolomite D = 2 directions @ 56/124 - goodGypsum E = 3 directions @ 90–(1-good; 2-poor)Biotite and Muscovite F = 3 directions @ 90 - perfectQuartz and Olivine G = 3 directions @ 60/120 - perfectFluorite H = 4 directions – perfectAmphibole VI. FRACTUREMinerals that break along curved or rough, uneven surfaces are said to fracture rather than cleave. Many minerals fracture in some directions and cleave in others. For example: Examine Orthoclase Feldspar. It cleaves in two directions, but fractures in the third. Examine Muscovite Mica. It cleaves in one plane, but fractures in any other In contrast, Quartz only has fracture surfaces, with no observable cleavage. Note: do not confuse the six-sided crystal-form faces of quartz for cleavage faces.Name another mineral that cleaves in two directions, but fractures in theName another mineral that cleaves in one direction, but fractures inName another mineral that has no cleavage - only fractureLook at your six-sided quartz sample. If it has been broken you will see that it did not break along a crystal face. Do not confuse the smooth, flat, six-sided form in which a crystal grows with a cleavage face. Quartz grows with no cleavage. Minerals that break leaving a rough surface are said to have an IRREGULAR FRACTURE. Minerals that fracture in a smooth, curved surface rather than a rough, uneven, blocky surface are said to exhibit CONCHOIDAL FRACTURE. Which type of fracture does your Quartz sample(s) show?Which type of fracture does your Feldspar sample(s) show?Quartz, Chalcedony, Jasper, and Chert are all forms of pure silica with similar physical properties. Silica is the name for the chemical compound SiO2. Quartz and chalcedony are minerals; jasper and chert are rock names.VII. CARBONATE MINERALSThe minerals Calcite (CaCO3), and Dolomite (Mg,Ca)2CO3 are very common in sedimentary and metamorphic rocks like limestone and marble, Three physical properties help set these minerals apart from others that might “look” like them: 1) hardness; 2) cleavage; and 3) reaction to dilute HCl acid (the acid test). You do not have HCl acid. You can use regular vinegar from your kitchen instead. You may need to use your hand lens to see the reaction.What is the hardness of the calcite?What is the cleavage of the calcite?The calcite mineral is light or dark-colored?THE ACID TEST: The expression "The Acid Test" has become a figure of speech in the English language. It indicates certainty. This expression comes from the test geologists use for carbonate mineral-like Calcite (CaCO3), and Dolomite (Mg,Ca)2CO3.Directions: Put a drop of vinegar on your calcite sample; observe the results (you may need to use your hand lens to see the results):Describe the result of the acid test. What do you think is happening?Chalk consists of very tiny shells made of Do you think you’d have the same reaction?Kaolinite looks a lot like chalk but is actually Do you think kaolinite would react with acid?VIII. EXAMINATION OF THE 24 MOST COMMON ROCK-FORMING MINERALSDirections: Carefully examine each of the following common minerals samples for their physical properties. A physical property that is exceptionally helpful in identifying a specific mineral has an “X”. Record only for those properties of each mineral that has a marked “X”.Luster: write M for metallic or NM for nonmetallicColor: write the shade of color presentHardness: S for soft (softer than 5.5) or H for hard (harder than 5.5)Cleavage:0 – no cleavage planes1 – 1 plane of cleavage2@90 – 2 planes at 90°2not@90 – 2 planes at different degrees than 90°3@90 – 3 planes at 90°3not@90 – 3 planes at different degrees than 90°Streak: color of powered mineral on the streak plateAcid test: “+” for if there is a chemical reaction with acid or “–“ for no chemical reactionMagnetic: yes or noOther: taste, smell, crystal form, or touchThen check your MINERAL DATABASE for the established physical property values and compare them to those that you determined.lustercolorhardnesscleavagestreakacidmagnetother1. graphiteX _____ ____X _____ ____ ____ ____ ____X touch______________2. galenaX _____X _____X _____ ____X _____ ____ ____ ____3. chalcopyriteX _____X _____X _____ ____X _____ ____ ____ ____4. pyriteX _____X _____X _____ ____X _____ ____ ____ ____5. magnetiteX _____X _____X _____X _____X _____ ____X _____ ____6. hematite (var. specular)X _____X _____ ____ ____X _____ ____X _____ ____7. gypsum ____ ____X _____X _____ ____ ____ ____ ____8. muscovite ____X _____X _____X _____ ____ ____ ____ ____9. biotite ____X _____X _____X _____ ____ ____ ____ ____10. halite ____ ____X _____X _____ ____ ____ ____X taste______________11. calcite ____ ____X _____X _____ ____X _____ ____ ____12. fluoriteX _____X _____X _____X _____ ____ ____ ____13. hematite (var. earthy)X _____X _____ ____ ____X _____ ____X _____ ____14. hornblende ____ ____X _____X _____ ____ ____ ____ ____15. augite ____ ____X _____X _____ ____ ____ ____ ____16. potassium (orthoclase) feldspar ____ ____X _____X _____ ____ ____ ____ ____17. plagioclase feldspar ____ ____X _____X _____ ____ ____ ____ ____18. olivine ____X _____X _____X _____ ____ ____ ____ ____19. actinolite ____X _____ ____X _____ ____ ____ ____ X crystal form ___________20. quartz (var. rock crystal) ____X _____X _____X _____ ____ ____ ____ X crystal form ___________21. quartz (var. milky) ____X _____X _____X _____ ____ ____ ____ ____22. chalcedony ____X _____X _____X _____ ____ ____ ____ ____23. tourmaline ____X _____X _____X _____ ____ ____ ____ X crystal form ___________24. garnet ____ ____X _____X _____ ____ ____ ____ ____IX. Written Laboratory ReflectionDirections: Write a reflection of the lab activity, explaining its purpose, the methods used, the results obtained, and a brief personal reflection of what you enjoyed and learned about doing this lab.What was the purpose of this lab? What did you actually discover and learn during this lab? What did you enjoy most about this lab? Also, what was challenging or thought-provoking?
