Analyze these two photomicrographs of ice crystals (snowflakes) by William Bentley.

How many crystals do you see in this sample? _____ List the number of different minerals in the sample and give a description of each one.

How many crystals do you see in this sample? _____ List the number of different minerals in the sample and give a description of each one:

How many crystals do you see in this sample? _____ List the number of different minerals in the sample and give a description of each one:

How many crystals do you see in this sample? _____ List the number of different minerals in the sample and give a description of each one:

B. Which of these samples seems to have crystals of a valuable chemical element? _______ What element? _______

C. rEFLECT & DISCUSS Based on your observations in this activity—what is a rock, and how are rocks related to minerals and crystals?

A c t i v i t Y 3.1 Mineral and rock Inquiry Name: ______________________________________ Course/Section: ______________________ Date: ___________

A. All of the samples below are rocks from Earth’s crust. Record how many crystals you see in each sample (Write 1, 2, 3, or many). Then make a numbered list of how many different kinds of minerals are in the sample and describe each one in your own words. Complete parts B and C.

M03_AGI4511_01_SE_C03.indd 101 12/10/13 1:54 PM

cbentley
Pencil
cbentley
Pencil
cbentley
Pencil

102

A. Indicate whether the luster of each of the following materials looks metallic (M) or nonmetallic (NM):

1. a mirror: __________ 2. butter: __________ 3. ice: __________ 4. a rusty nail: __________

B. What is the streak color (i.e., color in powdered form) of each of the following substances?

1. salt: ________________ 2. wheat: _________________ 3. pencil lead: ____________________

C. What is the crystal form (FIGURE 3.4) of the:

1. quartz in FIGURE 3.1B? __________________ 2. native copper in FIGURE 3.6? __________________

D. Look up quartz in the Mineral Database (FIGURE 3.21, page 93) to find a list of the varieties (var.) of quartz. Then identify each quartz variety below, and write its name beneath the image.

var. _________________ var. _________________ var. _________________ var. _________________

E. A mineral can be scratched by a masonry nail or knife blade but not by a wire (iron) nail (FIGURE 3.9).

1. Is this mineral hard or soft? _______________

2. What is the hardness number of this mineral on Mohs Scale? __________

3. What mineral on Mohs Scale has such a hardness? ____________________

F. A mineral can scratch calcite, and it can be scratched by a wire (iron) nail.

1. What is the hardness number of this mineral on Mohs Scale? __________

2. Which mineral on Mohs Scale has this hardness? ____________________

G. The brassy, opaque, metallic mineral in FIGURE 3.7A is the same as the mineral in FIGURE 3.8. What is this mineral’s hardness, and how can you tell?

H. Analyze the mineral samples and figure caption in FIGURE 3.16.

1. What is this mineral’s hardness (give a number or range of numbers)? _____________________________

2. Very carefully cut out the cleavage goniometer from GeoTools Sheet 1 at the back of this manual. Be sure to cut the angles as exactly as possible. Sketch the characteristic shape that this mineral breaks into. Using the cleavage goniometer, measure the angles between flat flat cleavage surfaces of this mineral in FIGURE 3.16, and record the angles here:

What is the name of this kind of cleavage?

I. A mineral sample weighs 27 grams and takes up 10.4 cubic centimeters of space. What is the SG (specific gravity) of this mineral? Show your work.

A c t i v i t Y 3.2 Mineral Properties and Crystals Name: ______________________________________ Course/Section: ______________________ Date: ___________

M03_AGI4511_01_SE_C03.indd 102 12/10/13 1:54 PM

103

0.1 mm

J. Analyze these two photomicrographs of ice crystals (snowflakes) by William Bentley.

1. Based on FIGURE 3.4, what is the crystal form of the top crystal?

2. Notice that the crystals are symmetrical, but not exactly. Imperfections are common in crystals, but their underlying crystal form can still be detected. To what crystal system in FIGURE 3.5 do ice crystals belong? How can you tell?

3. rEFLECT & DISCUSS The habit of snowflakes (crystals of water ice) includes a variety of different crystal forms. Why don’t all snowflakes have the same crystal form?

K. Analyze each crystalline household material pictured below and identify which crystal system it belongs to. (Use a hand lens or microscope to observe actual samples of the materials if they are available.)

1 cm

Sucrose Epsomite Halite