Crystalline Structures Lab Materials: Pencil, Crystal Models, Dictionary
# of pairs and name of shapes that make-up Crystal name sides Name Meaning
1. CUBE
2. TETRAGON
3. ORTHORHOMBIC
4. RHOMBOHEDRAL
5. MONOCLINIC
6. TRICLINIC
7. HEXAGONAL
Short Answer Compare: A. A cube to a Tetragon.
B. An Orthorhombic Crystal to an Rhombohedral one.
C. A Monoclinic Crystal to a Triclinic Crystal. Mineral Identification Activities Crystal Shapes Use a hand lens to look at halite and magnesium sulfate crystals. Draw one crystal of each sample. Compare the two crystals. How are they alike? Different? What is the crystal name for each shape? Drawing Crystal Name Halite
Magnesium Sulfate
What is the True Color of a Mineral? Examine samples of magnetite and hematite. Both minerals contain iron. Describe the color and appearance of the two minerals. How are they similar and different? Rub the hematite across an unglazed ceramic tile. Observe the color of the steak on the tile. Rub the magnetite across the tile. Observe the color of the steak on the tile. Mineral Streak Color Hematite
Magnetite
Does the color of each minerals steak match the color of the mineral?
How could this steak test be helpful in identifying these as two different minerals? Special Physical Properties There are some minerals that are more easily identified due to special properties. To test for these properties use Magnetite, Calcite and Fluorite. To test for magnetism use a compass and pass the minerals over a compass. A mineral with high amounts of iron will cause the compass needle to move and is a magnetic mineral. To test for fluorescence use an ultra-violet (UV) light and hold the three minerals in the light. A mineral that has the property of fluorescence will glow. To test for a reaction to acid place a drop of the acid solution on each of the minerals. The reaction will be a fizzing of the mineral and gases being released into the air. Which mineral has these properties: Magnetism Fluorescence Reacts to acid Moh’s Hardness Scale Pick up the baggie of 9 unknown mineral samples. Using the testing methods on the chart, place the minerals in order of hardness. When correct have your lab sheet signed.
Talc 1 Flakes easily when scratched by a fingernail. Gypsum 2 Will scratch with a fingernail. Calcite 3 Not scratched by a fingernail. Copper penny will scratch. Fluorite 4 Easily scratched by an iron nail. Apatite 5 Scratched by an iron nail. Felspar 6 Cannot by scratched by an iron nail. It can scratch window glass. Quartz 7 Can scratch hard glass easily. Can scratch Feldspar. Topaz 8 Can scratch Quartz. Corundum 9 Can scratch Topaz The Density of Minerals Check to make sure the mineral samples of Pyrite, Quartz and Galena are small enough to fit in the graduated cylinder. Place each mineral sample individually on the balance and record its mass in the data table. Fill the cylinder with water to the 50-ml. mark. Carefully place one sample into the cylinder of water. Try not to spill any of the water. Read the level of the water on the scale of the graduated cylinder. Record the level of the water with the sample in it. Calculate the volume of water displaced by the sample. To do this, subtract the volume of water without the sample from the volume of water with the sample. Record your answer. Calculate the density of the samples by using this formula.
Mass of Mineral______Density = Volume of water displaced by the mineral
Data Table Pyrite Quartz Galena Mass of the Mineral (g) Volume of water 50 50 50 without mineral (ml) Volume of water with Mineral (ml) Volume of water displaced (ml) Density (g/cm3) Analyze and Conclude 1. Which mineral had the highest density? The lowest density?
2. How does finding the volume of the water that was displaced help you find the volume of the mineral itself?
3. Why won’t the procedure you used in this lab work for a substance that floats or one that dissolves in water?
4. Pyrite is sometimes called “fool’s gold” because its color and appearance are similar to real gold. How could a scientist determine if a sample was real gold?
5. Does the shape or size of a mineral sample affect its density? Explain.