Learn The Great Basin
Sam D. Macaluso
SPECIFIC GRAVITY OF NEVADA MINERALS
GOAL-Have students determine if the specific gravity of Nevada minerals is the same or nearly the same as the specific gravity of similar minerals listed in a rock and mineral book.
OBJECTIVE-Students will demonstrate knowledge of determining the specific gravity of various minerals by testing them three separate times
MATERIALS-scale; water; beakers (10 ml, 25 ml, 125 ml, 250 ml); Nevada minerals samples (i.e., pyrite, magnetite, calcite, barite, malachite, grossular, galena, fluorite, etc.); calculator; paper or recording journal; markers; pencils; rock and mineral book showing mineral specimens and specific gravities.
PROCEDURE-
1. Discuss what specific gravity is with the class. Specific gravity is the weight of a mineral in relation to the weight of the same volume of water. A specific gravity of 2.5 means it is 2_ times heavier than water. Specific gravity is used to help distinguish similar looking minerals.
2. Test the mineral's specific gravity 3 separate times in the following manner:
a. Weigh mineral on scale in grams and record on paper or recording journal.
b. Weigh either 10 ml or 25 ml beaker without water and record.
c. Fill 125 ml beaker with 100 ml of water or 250 ml beaker with 200 ml of water.
d. Place mineral into either the 125 ml or 250 ml beaker with water.
e. Note rise in level of water in beaker after putting in mineral and mark water level with marker.
f. Pour excess water from 125 ml or 250 ml beaker into 10 ml or 25 ml beaker. Be sure 125 ml beaker is at 100 ml of water or 250 ml beaker is at 200 ml of water.
g. Weigh 10 ml or 25 ml containing excess water and record on paper or recording journal.
h. Subtract weight of beaker with water from weight of beaker without water and record difference.
i. Using a calculator determine the specific gravity of the mineral. Take the weight of the mineral divided by the difference in water weight (from Step h)=(equals) the specific gravity of the mineral. Record results.
3. Conduct the specific mineral test 3 separate times using the same mineral.
4. Record the specific gravity of each test.
5. Refer to the rock and mineral book and find the same mineral being tested and record its specific gravity.
6. Take an average of the results:
a. Add the recorded specific gravity of each of the 3 tests and total
b. Divide the total by 3=(equals) the average specific gravity of the mineral.
c. Compare the average of the 3 tests to the listed specific gravity in the rock and mineral book.
NOTE: A specific gravity test is conducted 3 separate times to make sure that the specific gravity of the mineral is as accurate as it can be.
Using only 1 test can leave a large margin for error.
CULMINATION-
1. Have the class make observations between the specific gravity of their mineral and the specific gravity listed in the rock and mineral book.
a. If the specific gravity of the mineral is the same or very nearly the same as that listed in the book ask students why they think that is the case. (Answers should reflect that the specimen is pure enough to have same specific gravity.)
b. If the specific gravity of the mineral is different from the specific gravity listed in the book ask students why they think that is the case. (Answers should reflect that the specimen was not pure; there may be another mineral besides the one being tested, the specimen is not solid).
ASSESSMENT-Proper completion of the tests, calculation and answers to culmination questions.