UNIVERSITY OF SOUTH ALABAMAStereo projections Now envision the equatorial cross section of the...
13
GY 302: Crystallography & Mineralogy UNIVERSITY OF SOUTH ALABAMA Activity 2: Stereonets (Assignment 2)
UNIVERSITY OF SOUTH ALABAMAStereo projections Now envision the equatorial cross section of the spherical projection. There are 2 possible stereonet configurations: 1) Wulff Net (equal
1. Stereo Projections and the Wulff Net 2. Stereo projections of
the Point Groups
Stereo projections
Envision the cube suspended in a sphere
Stereo projections
Now pass a line that is perpendicular to each crystal face
(poles) outward to intersect the sphere
001
001
010
010
001
Stereo projections
Now envision the equatorial cross section of the spherical
projection. There are 2 possible stereonet configurations: 1) Wulff
Net (equal angles) 2) Smith Net (equal area)
Projection:Equal AngleRadius:3.50 inches
Wulff NetN
S
W E
10
170
350
190
20
160
340
200
30
150
330
210
40
140
320
220
50
130
310
230
60
120
300
240
70
110
290
250
80
100
280
260
0 DATA
Source: D. Allison
Stereo projections
010
001
100
100 010 and 001 Faces
010 010
Stereo projections
001 111/111
111/111 111/111
111/111
The stereonet allows for precise measurements of angular
relationships between crystal faces
Stereo projections
001
All faces are 90° apart from one another…
-45°
45°
90° 0°
Stereo projections
001
All faces are 90° apart from one another… 90°
90° 90°
Stereo projections
010
001
…and rotated 45° from the faces of a cubic form
45°
45°
Chalk Board
The Point Groups •Orthorhombic Point Groups; 2-fold rotational
axes or 2 fold-rotational axes and mirror planes
Projection:Equal AngleRadius:3.50 inches
Wulff NetN
S
W E
10
170
350
190
20
160
340
200
30
150
330
210
40
140
320
220
50
130
310
230
60
120
300
240
70
110
290
250
80
100
280
260
0 DATASource: D. Allison
Today’s Homework 1. If necessary, schedule a help session
2. Stereonet assignment 3. Lecture test 1 (take home) issued
next Tuesday
Today’s Lab 1. Quiz One in a few minutes
2. Assignment 1: Isometric/Hexagonal models due now
On Line 1. Polymorphism, pseudomorphism and habit (Lecture
6)
2. Next Tuesday… take-home crystallography test
Slide Number 1Last Time #1 (Thursday Lecture)Slide Number 3Slide
Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number
8Slide Number 9Slide Number 10The Point GroupsSlide Number
12Today’s Homework
