LAB 1- Minerals

LAB 1: MINERALS IDENTIFICATION Objectives:  Learn the names and basic properties of the common rock-forming minerals  Learn about mineral occurrence vs a mineral’s crystal shape Identification of Minerals A mineral is a substance that is inorganic, naturally occurring, crystalline (not glassy—meaning there is a regular arrangement of atoms in an array), and solid with a particular chemical composition. Minerals can appear in nature as beautiful geometric crystals or as lumpy, irregular masses. Minerals crystals can be microscopically small or bigger than a truck. In rocks, minerals often appear as small blotches of color, sometimes with clear geometric shapes and sometimes as little blobs. There are thousands of minerals, but only about a dozen occur most commonly in rocks on and near the surface. These most-common minerals are referred to as the rock-forming minerals. The following are the characteristics to which you should pay particular attention: Color —an obvious characteristic, although one that can deceive; one common mineral, quartz, can be found in just about any color. Transparency —is also referred to as diaphaneity. Minerals may be transparent, translucent, or opaque. Luster —how a mineral interacts with light. Terms used are metallic, submetallic, adamantine (brilliant), dull, greasy, pearly, resinous, silky, waxy, and vitreous (glassy). Special interactions may include asterism (a star inside the crystal), chatoyancy, color change (pleiochroism), aventurescence (glittery), and schiller (iridescence). Hardness —mineral hardness is gauged on a scale of 1 (soft) to 10 (hard as diamond). To test hardness, scratch the mineral with common objects such as your fingernail (about 2-3), a penny (about 5), glass (6), or a knife (5-6). Quartz, for example, has a hardness of 7. Streak —is the color of the powder left behind when you drag the mineral across a porcelain tile. Minerals harder than the tile may have “no” streak. Fracture —is the way a mineral breaks. Some minerals tend to break along planes of weakness, known as cleavage planes. Others do not. Instead, they break in an irregular fashion. Fracture can be described as hackly (like soil), uneven, splintery, or conchoidal (scoop-shaped breaks like glass). Tenacity —is a mineral’s reaction to stress. It may break, tear, crumble, flex, or fracture in a particular way. Fusibilty —is how easily a small, 1.5mm splinter or fragment of a mineral sample melts (fuses) in a flame. The flame used is either a candle or a blowtorch or blowpipe. Fusibility is often recorded numerically. A fusibility of 1 means even a large fragments melts readily in a candle flame. A fusibility of 2 means the fragment must be 1.5mm or smaller to melt. A fusibility of 3 means the fragments edges round in a candle flame, but melt with a blowtorch. A fusibility of 4 means the fragments edges melt with a blowtorch. A fusibility of 5 means the edges barely melt with a blowtorch. A fusibility of 6 means only the thinnest edges melt with a blowtorch. A fusibility of 7 means no melting at all with a blowtorch.

Occurrence/Crystal habit —the apparent shape of the crystals or how the crystals group together. Well- developed crystals are described as euhedral. However, if the crystals are tiny, microscopic or massed together, a crystal shape may not be visible to the naked eye. There are many names for crystal habits shown on the websites and apps listed as resources. Specific Gravity —is the density of the mineral divided by the density of water. A specific gravity of 1 would indicate a mineral that is as dense as water. A specific gravity of 2-3 is typical for many minerals. Anything larger is quite dense. Dark-colored, iron-bearing minerals are typically denser than lighter- colored minerals that contain little or no iron or other heavy elements. To measure specific gravity, follow this procedure: 1) Turn on and zero a scale. 2) Make sure the scale is weighing things in grams (g). 3) Weigh the dry mineral specimen and record its weight in grams. 4) Fill a cup with just enough water to submerge your specimen. 5) Weigh the water-filled container and zero the scale. 6) Submerge the mineral in water completely by lowering it in with a paper clip or using tweezers. Do not allow your mineral sample to touch the sides of the container. 7) Record the weight of the submerged sample in grams. 8) Divide the dry weight of the sample by the weight of the submerged sample and that is the specific gravity. Cleavage —is the tendency for a mineral to break along one or more planes. A mineral may show perfect, imperfect, good, or poor cleavage in one or more directions. http://csmres.jmu.edu/geollab/fichter/Minerals/cleav age.html Crystal system and class —is a technical description of the symmetry of the crystal shape (if a good example can be seen). There are 7 crystal systems (shown below) and 32 crystal classes.

From: https://geology.com/minerals/rock-forming-minerals/ Relative abundance percentages from Ronov and Yaroshevsky; Chemical Composition of the Earth's Crust ; American Geophysical Union Monograph Number 13, Chapter 50, 1969. 4

This chart shows the relative abundance of the common rock forming minerals in some of Earth's most abundant rock types. Basalt and gabbro account for most of the rock in the oceanic crust, granite (rhyolite) and andesite (diorite) represent abundant rock types of the continental crust. Sandstone, shale and carbonates represent the common materials in the sedimentary cover of continents and ocean basins. From: https://geology.com/minerals/rock-forming-minerals/ On the following pages, fill in the blanks to find the information for each of the important rock-forming minerals below. (know how to identify each in a photo on the exam) 5

Lab 1: Introduction to Mineral Properties (Moh’s Scale Kit) Hard- ness Luster Color Streak Cleavage # Or fracture Any Miscellaneous Properties Name 7 NM : vitreous or greasy Various white No Cleavage Conchoidal Fracture Many colors : white, clear, grey, pink, purple, green, etc. Striations on crystal faces Quartz 8 vitreous Yellow, Brown, Pink and blue colorless No cleavage Six sided crystals with striated faces and pointed ends Topaz 9 vitreous brown White No cleavage Six sided crystals Corundum

Mineral Identification Table: TABLES FOR THE IDENTIFICATION OF MINERAL UNKNOWNS MINERAL IDENTIFICATION TABLES The table that follows is intended to help you identify the mineral unknowns that you will be studying during this class. All of the minerals you will study are contained in this table. Diamond is listed, although you will not see it in this class. This table is arranged in two parts: Part 1: Minerals with Non-Metallic Luster Part 2: Minerals with Metallic Luster (the last five minerals) Igneous Minerals 1. Augite 2. Biotite 3. Hornblende 4. Magnetite 5. Muscovite 6. Olivine 7. Plagioclase Feldspar 8. Tourmaline Sedimentary Minerals 9. Calcite (variety chalk) 10. Halite 11. Kaolinite 12. Limonite (var. bog ore) Metamorphic Minerals 13. Actinolite 14. Epidote 15. Garnet 16. Glaucophane 17. Kyanite 18. Serpentine Ore Minerals 19. Azurite & Malachite 20. Chalcopyrite 21. Galena 22. Graphite 23. Hematite (massive) 24. Pyrite 25. Sulfur 8

Mineral Identification Table: # Hardness Luster Color Streak Cleavage # or fracture Any Miscellaneous Properties Name 8 3 vitreous White White 3 perfect cleavage not 90- degree angle Reacts with HCI, rhombic cleavage Calcite 9 2.0-2.5 vitreous Clear to light yellow yellow Perfect cleavage in 1 thin sheets, forms flexible, transparent Muscovite 10 6.5-7.0 vitreous Olive green Green No cleavage granular Olivine 11 2.0-2.5 Dull White to tan White streak Yes cleavage Earthy odor, powedery Kaolinite 12 5.5-7.5 vitreous White White Yes cleavage 90 degree angle Greasy feel Actinolite 13 7.0 vitreous Red or brown White No cleavage 12 sided crystal Garnet 14 5.0-7.0 vitreous Bluish-gray Blue Yes cleavage Blade shaped crystals kyanite 15 5.0 Dull to greasy Black Green No cleavage Slight greasy feel, massive fibrous Serpentine 10

Mineral Identification Table: # Hardness Luster Color Streak Cleavage # or fracture Any Miscellaneous Properties Name 16 3.4-4.0 vitreous Grass green Green streak Yes cleavage Occurs as surface coating, masses or tiny crystals Azurite & Malachite 17 2.5 vitreous Silver gray Gray Perfect cubic cleavage heavy Galena 18 5.0-6.0 Dull Reddishbro wn to black Red-brown No cleavage Massive Hematite 19 6.0-6.5 vitreous Brass yellow Greenish black No cleavage Cubic crystals with striations Pyrite 20 1.5-2.5 vitreous Yellow Yellow No cleavage No cleavage Sulfur 21 6.0-6.5 vitreous gray white 2 planes not at 90 degree angle No cleavage Tourmaline 22 3.5 -4 metallic Brass yellow Greenish black Indistinct magnetic on heating Chalcopyrite 23 4-5.5 Earthy brown and yellow Yellowish brown No cleavage No cleavage Limonite (var. bog ore) 11

Mineral Identification Table: 13