Materials Included In Kit

Additional Materials Required

Prelab Preparation

1. Each mineral sample should be labeled with the appropriate number using a permanent marker, disc labels and superglue.
2. Label each mineral as follows:
   {12601_Preparation_Table_2}
3. The fishing line should be cut into 1-foot pieces before use.
4. Make copies of the Mineral Characteristics Data Table for individual student use in Part 8.

Safety Precautions

Aluminum chloride and copper(II) sulfate are slightly toxic by ingestion and are body tissue irritants. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron when performing Part 1. Wash hands thoroughly with soap and water before leaving the laboratory. Follow all laboratory safety guidelines.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures governing the disposal of laboratory waste. The products from Part 1 may be disposed of down the drain with an excess water according to Flinn Suggested Disposal Method #26b. All other materials may be saved for future use or disposed of according to Flinn Suggested Disposal Method #26a.

Teacher Tips

• Enough materials are provided in this kit for 28 students working in pairs, or for 14 groups of students. The laboratory activities can reasonably be completed in two 50-minute class periods. Set up three spring scale stations for Part 2.
• After several days, the sodium silicate solution used in Part 1 may become cloudy. If desired, carefully replace the solution with tap water to preserve the colorful silicate gardens.
• An excess of fishing line has been provided in this kit for multiple tests in Part 2.
• Actual mineral sample characteristics may vary slightly from the descriptions given on the Mineral Characteristics Data Table due to slight impurities.
• Set up a classroom data table for students to record the specific gravity of their samples. Average the specific gravity values to obtain the classroom specific gravity values for each mineral. To save time, you may wish to have each student group focus and perform the remaining tests for one or two minerals and then gather the information in an all-inclusive classroom data table as well.
• You may wish to supplement your students knowledge of specific gravity and density with the following information:
  
  Density is an intensive physical property of matter—that is, it is a property unique to each substance (at a specified temperature) and can therefore be used to distinguish one substance from another. An unknown substance is often identified by determining its density and comparing this experimental value to the actual density recorded in chemical literature. The density of a substance is defined as the amount of matter in a given unit of space, also thought of as the “concentration” of a substance. Density is calculated as the ratio of mass to volume, where mass is the amount of matter in an object (given in grams) and volume is the amount of space the object occupies (given in milliliters or cubic centimeters). The equation to calculate density is as follows:
  {12601_Tips_Equation_2}
  Densities vary with temperature and pressure. The standard for comparing densities is water, which at 4 °C, has a density of almost exactly 1.00000 grams per milliliter (0.999973). Note: Water attains its maximum density of 1.00 g/mL at 4 °C.
  
  Specific gravity is a term often used interchangeably with density. Specific gravity is the ratio of the density of a substance to the density of an equal volume of a reference substance (water) at 4 °C or other specified temperature. Specific gravity is an abstract number, which has no units. Since the density of water is 1.00 g/mL at 4 °C, then for solids and liquids, specific gravity is numerically equal to density (except without the units).

Sample Data

Part 1

Drawing/Observations

Part 2 Parts 3, 4, 5, 6 and 7

Please see the Mineral Characteristics Data Table for sample data.

Part 8

Answers to Questions

Part 1

1. Compare and contrast the crystals formed in this activity with minerals.

   They are solid, inorganic and have a definite chemical composition. They do not, however, occur naturally.

2. Compare your results to your classmates. How are the results similar? How are they different?

   Answers will vary.

3. List at least three possible factors that may affect the formation and growth of mineral crystals in this activity.

   Temperature, amount of solid chemical, time, etc.

Part 2

1. Which of your two minerals had the highest specific gravity?

   Answers will vary.

2. Most metallic minerals have a specific gravity greater than 5.0 and non-metallic minerals have a specific gravity around 3.0. Given your specific gravity results, are your samples considered metallic or nonmetallic?

   Answers will vary.

3. What possible errors may occur in this activity?

   Error in mass measurement, impurities in the minerals, etc.

Part 3

1. Compare at the results obtained for samples 10, 11 and 12. These samples are the same mineral. What similarities or differences are observed?

   They are all nonmetallic, but they are all different in color.

2. Compare the color and luster of samples 3, 6 and 11. Explain why color is not the best way to classify minerals.

   The colors of all of these samples are very similar. This shows that color alone cannot be used for identification of minerals.

3. Select three minerals that have unique colors that would be helpful in the identification process. List the mineral samples and explain why the color would be helpful in identification.

   Sulfur (13) has a unique yellow color. The different colors of quartz (10, 11, 12), such as the pink in rose quartz (12), are helpful in identifying the type of this mineral.

Part 4

1. Which minerals could possibly be used for the panes of windows?

   Possibly minerals 5 (fluorite), 11 (milky white quartz) and 12 (rose quartz).

2. Which minerals could be used in situations where the blockage of light is needed?

   All other minerals besides 5, 11 and 12 may be used to block light.

Part 5

1. Describe what a mineral streak is.

   A streak is the color of a mineral’s powder.

2. List examples of factors that could affect the color of a mineral’s streak.

   Contact with air, water and impurities in the mineral.

3. Were all of the streaks the same color as the minerals? If not which ones were different?

   No. Some, such as fluorite (5) and the quartz samples (10, 11, 12) have no streak. Biotite (2) looks black but has a light brown streak.

Part 6

1. Define mineral hardness.

   Hardness is how resistant a mineral is to being scratched.

2. List the mineral samples tested in order from softest to hardest.

   14, (13, 6), 2, (3, 4), (1, 5), (7, 8), 9, (10, 11, 12)

3. What is the hardest known mineral on Earth?

   Diamond

Part 7

1. Define cleavage.

   Cleavage is how a mineral splits or breaks.

2. Given your observations, which mineral samples could be easily divided into smaller pieces with the same or similar shapes or characteristics?

   Answers will vary. Samples 2, 3 and possibly 1, 5, 6 and 14.

Teacher Handouts

12601_Teacher1.pdf

Introduction

What is a mineral? How are minerals formed? In this activity, minerals will be identified based on their physical properties, including color, luster, hardness, cleavage and streak. The specific gravity of the minerals will be determined and mineral crystals will be formed.

Concepts

• Mineral formation
• Streak
• Cleavage
• Hardness
• Specific gravity

Background

Minerals are natural compounds formed through geological processes. The term “mineral” includes not only the material’s chemical composition, but also its structure. Minerals range in composition from pure elements and simple salts to very complex silicates with various forms. To be considered a mineral the following five criteria must be met.

A mineral must:

• Be a solid
• Occur naturally
• Be inorganic (never alive!)
• Have a definite chemical composition
• Have its atoms arranged in an orderly (crystalline) pattern

There are more than 250 different minerals on Earth! The following list provides background information and describes common uses of the minerals that will be tested in this activity.

Azurite
Azurite is a soft blue copper mineral produced by weathering of copper ore deposits. It is used as a blue pigment and occasionally in jewelry and beads.

Biotite
Biotite is a mineral consisting of iron, magnesium, aluminum, silicon, oxygen and hydrogen sheets that are bonded together by potassium ions. Biotite is used to obtain the relative ages of rocks (through argon dating) and it is mined for mineral collection purposes.

Calcite
Calcite is a mineral consisting largely of calcium carbonate and is the second most abundant mineral on Earth. Calcite uses include animal feed, antacids, chemical industry, dough strengthener, decorative stone in buildings and statues, building construction, filler in baking powder, glass industry, manufacturing of paper, optical purposes, photography, statues and waste treatment.

Copper
Azurite, chalcopyrite and malachite are ores of copper which are used in the manufacturing of brass, bronze, coins, jewelry, cooking utensils and pigments. Most of the wiring in electrical appliances (e.g., TVs, stereos, computers, telephones, aircraft, satellites, automobiles, residential wiring, plumbing) is also made from copper. Malachite also provides shades of green used in making cosmetics and was used by earlier people for making paint used on their clothing, faces and cave walls.

Fluorite
Fluorite is the mineral form of calcium fluoride (CaF₂), that is used in the production of hydrofluoric acid and the source of the “fluoride” in toothpaste. It is used in the pottery, ceramics, optical, electroplating and plastics industries; in the metallurgical treatment of bauxite to make aluminum; as a flux to remove impurities in the manufacture of steel; in carbon electrodes, emery wheels, electric arc welders and as paint pigment.

Gypsum
Gypsum is a hydrated calcium sulfate whose primary use is in the manufacture of “Sheetrock™” or wallboard. The walls in homes, offices and schools are usually at least partly constructed using a gypsum board.

Limonite
Limonite is an ore consisting of a mixture of hydrated iron(III) oxide and hydroxides. It is most commonly yellowish-brown and is mined as ore for the production of iron.

Magnetite
Magnetite is the principal ore of iron which is used in making steel, nails, kitchen appliances, furniture, tools, bridges, buildings, automobiles, construction equipment, manufacturing machinery, highway construction, shipbuilding, trains, railroads etc. Powdered iron is used in magnets, high-frequency cores, and auto parts and as a catalyst. Radioactive iron (iron 59) is used in medicine and as a tracer element in biochemical and metallurgical research. Iron blue is used in paints, printing inks, plastics, cosmetics and paper dyeing. Black iron oxide is used as a pigment and in polishing compounds, medicines and magnetic inks.

Pyrite
Pyrite (also known as fool’s gold) is an iron sulfide mineral used in the manufacture of sulfur, sulfuric acid and sulfur dioxide. Pellets of pressed pyrite dust are used in the recovery process of iron, gold, copper, cobalt and nickel. It is also used to make inexpensive jewelry.

Quartz
Quartz, crystalline silicon dioxide or silica, is used in laboratory tubes, crucibles, glass, digital watches, radios, TVs, radar, sandpaper and in construction and foundry molds. It is also used in jewelry and other gem uses. Sulfur Sulfur is used in the manufacture of fertilizer, sulfuric acid, in papermaking, film, tires, paint, detergents, explosives, matches, drugs and dyes.

Talc
Talc is a mineral composed of hydrated magnesium silicate. It is used in stoves, sinks, electrical switchboards, as a lubricant and in baby powder. It is also used as a food additive and in pharmaceutical products.

Experiment Overview

Part 1. Mineral Formation
Metallic salts will be added to sodium silicate solution. In a matter of seconds, mineral crystals form and sprout upwards from the bottom of a cup before your eyes. The mineral crystals will continue to form over several days.

Part 2. Specific Gravity
Archimedes discovered that the weight of a body in air minus its weight in water is equivalent to the weight of the water displaced by the body. Specific gravity is defined as the weight of a body compared with the weight of an equal amount of pure water at 4 °C (4 °C is the temperature at which water is densest). When a body is placed in water, the volume of water displaced is equal to the volume of the body. When the body is placed in water, it undergoes an apparent loss of weight. This loss of weight is equal to the weight of the water displaced. When a mineral is weighed in air and then weighed in water, the loss of weight is equal to the weight of its volume in water displaced. The weight of the mineral in air divided by the loss of weight in water gives the specific gravity of the mineral.

Part 3. Color and Luster
Color is one of the most obvious characteristics of a mineral. Even though the color of a mineral may be very noticeable, there are several different reasons why minerals cannot be classified on color alone—many different minerals may have the same color, trace impurities may give minerals different colors, and minerals may rust or tarnish changing their original colors. The luster of a mineral refers to the way light is reflected from the mineral’s surface. There are two main types of luster—metallic and non-metallic. A mineral with a metallic luster shines like a piece of polished metal whereas a non-metallic mineral does not. The color and luster of 14 minerals will be observed and recorded.

Part 4. Light Interaction
The way that light bounces off or passes through a mineral tells something about how the atoms inside the mineral are arranged. The atoms in some minerals let light rays pass through, while some minerals have arrangements that make the light bounce right off. Each mineral will be studied to determine if each is opaque, translucent or transparent.

Part 5. Mineral Streak
The “streak” of a mineral is the color of the mineral’s powder. The streak of a mineral may be different than the color of the mineral itself. Sometimes the color of the outside of a mineral is changed by contact with the air, water and other minerals in the ground. Each mineral will be streaked on a ceramic streak plate to determine the streak color.

Part 6. Mineral Hardness
Hardness describes how resistant a mineral is to being scratched (this is different than breaking or shattering a mineral). Hardness is determined by either scratching the mineral or using the mineral to scratch something else. A geologist named Friedrich Mohs developed a scale for rating the hardness of minerals. The higher the number, the harder the mineral, with 10 being the hardest. Each mineral will scratch those with a lower hardness number, but will not scratch minerals with a higher number.

A steel nail, copper penny and a ceramic streak plate will be used to determine the hardness of each mineral.

Part 7. Mineral Cleavage
Cleavage describes how a mineral splits or breaks. Some minerals form perfectly flat surfaces when they break, others break or fracture into irregular pieces. Each mineral will be studied to determine if it has perfect, good or poor cleavage.

Materials

Safety Precautions

Aluminum chloride and copper(II) sulfate are slightly toxic by ingestion and are body tissue irritants. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron when performing Part 1. Wash hands thoroughly with soap and water before leaving the laboratory. Follow all laboratory safety guidelines.

Procedure

Part 1. Mineral Formation

1. Using a graduated cylinder, measure out 40 mL of water and transfer it to a plastic cup.
2. Using a graduated cylinder, measure out 25 mL of sodium silicate solution and transfer it to the cup. Gently stir the solution with a stirring rod.
3. With the use of a teaspoon sprinkle about ¼ teaspoon of each of the metallic salts—aluminum chloride and copper(II) sulfate—into the cup. Sprinkle the crystals out evenly. Cover the cup with plastic wrap.
4. Observe the colorful silicate crystals. They will start to grow within a couple of minutes and will continue for several days.
5. Sketch the mineral crystal formation and record all observations in the Mineral Data Table.
6. Answer the questions for Part 1.

Part 2. Specific Gravity

1. Obtain two different mineral samples. Record the number of the samples in the Mineral Data Table.
2. Tie one end of a 1-foot piece of fishing line around one of the minerals (see Figure 1).
3. Tie the other end of the string around the hook of a spring scale (see Figure 2).
   {12601_Procedure_Figure_1and2}
4. Record the weight of the mineral sample as Weight in Air (in grams) in the Mineral Data Table.
5. Obtain a plastic cup half full of tap water.
6. Fully immerse the mineral in the tap water.
7. Record the new weight shown on the spring scale as Weight in Water in the Mineral Data Table.
8. Subtract the mineral Weight in Water from the Weight in Air. This value will be the loss of weight in water. Record this value in the Mineral Data Table.
9. Divide the weight of the mineral in air by the loss of weight in water as shown in Equation 1. The resulting value is the specific gravity of the mineral. Record this value in the Mineral Data Table.
   {12601_Procedure_Equation_1}
10. Repeat steps 2–9 for the second mineral sample. The fishing line may be reused for the second mineral.
11. Record the specific gravity of the two mineral samples in the classroom data table.
12. Use the classroom data to calculate the average specific gravity value for each mineral in the Mineral Data Table for Parts 3, 4, 5, 6 and 7.
13. Answer the questions for Part 2.

Part 3. Color and Luster

1. Observe the color and luster of each mineral sample 1–14.
2. Study all sides of each mineral and record the color(s) of each in the Mineral Data Table.
3. Record the luster of each mineral sample as metallic or non-metallic in the Mineral Data Table as well.
4. Answer the questions for Part 3.

Part 4. Light Interaction

1. Look carefully at each mineral and decide if each is opaque, translucent or transparent.

   Use the following definitions to classify each mineral:
   Opaque—No light can pass through the mineral. When the mineral is held up to a light, no light shows through.
   Translucent—Some light can pass through, but you can’t see through the mineral. A mineral is translucent if the edges look lighter when it is held up to a light.
   Transparent—Light rays can pass right through the mineral. Transparent minerals look like glass—you can see right through them.

2. Answer the questions for Part 4.

Part 5. Mineral Streak

1. Obtain a white streak plate.
2. Take each mineral sample and rub it once or twice on the streak plate.
3. Record the color of the powder that rubs off each mineral in the Mineral Data Table.
4. Answer the questions for Part 5.

Part 6. Mineral Hardness

Note: Safety goggles should be worn for this activity.

1. Obtain a mineral sample and a steel nail. Try to scratch the surface of the mineral with a steel nail (hardness = 5). If the steel nail can scratch the mineral, the mineral’s hardness is less than 5. If the steel nail cannot scratch the mineral, the mineral’s hardness if greater than 5.
2. If the mineral’s hardness is less than 5, try to scratch the mineral with a copper penny (hardness = 3) and with your fingernail (hardness = 2). Determine the hardness of the mineral.
3. If the mineral’s hardness is greater than 5, try to scratch the mineral with a ceramic streak plate (hardness = 7). Determine the hardness of the mineral.
4. Repeat steps 1–3 with the remaining minerals. Record the hardness of each mineral in the Mineral Data Table.
5. Answer the questions for Part 6.

Part 7. Mineral Cleavage

1. All of the minerals being tested have already been broken from larger pieces. Using a magnifying glass, look at the broken surfaces on each mineral sample and describe the mineral’s cleavage.

   Use the following definitions to describe each mineral.
   Perfect Cleavage—The broken surface is perfectly flat. Light reflects off the surface when the mineral tilted back and forth.
   Good Cleavage—Some of the broken surfaces appear perfectly flat. When the mineral is tilted back and forth in the light, there appears to be one position that reflects light very well.
   Poor/No Cleavage—The broken surfaces are irregular. Although the mineral might be shiny, none of the surfaces are perfectly flat.

2. Record all descriptions in the Mineral Data Table.
3. Answer the questions for Part 7.

Part 8. Mineral Identification

1. Obtain a copy of the Mineral Characteristics Data Table from the teacher.
2. Using your test results from Parts 2–8, identify each mineral sample. Note: Some values may not be exactly the same due to experimental error or variance of the mineral samples.
3. Record the identity of each mineral sample in the Mineral Data Table for Part 8.

Student Worksheet PDF

12601_Student1.pdf