Determining axial ratio of crystal axes from stereographic projection
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Imagine a line perpendicular to face of crystal to surface of sphere.
Faces above equatorial plane project to top and� then are plotted on equatorial plane in a projection to the south pole� shown as closed symbols.
Faces below equatorial plane project to bottom then are plotted on equatorial plane in a projection to the north poleshown as open symbols.
Those with vertical faces plot on circumference.
Crystals faces are plotted based on angles measured from crystals.
Easiest is to plot using two angles:
Think of as latitude and longitude on a globe, location of cities � but distribution of cities don�t have symmetry.
a) Distance along circumference � along great circle � like longitude � indicated as f - theta.
b) Distance from center � along small circle � like latitude � indicated as r - phi.
Look at plotting Ithaca on globe - f = 76�, r= 48� (90 - 42).
Plotting facilitated by use of stereographic projection.
Types of projection � for crystallography use an equal angle net � Wulff net.
In structural geology, use an equal area net - Schmidt net.
Faces above equatorial plane project to top and� then are plotted on equatorial plane in a projection to the south pole� shown as closed symbols.
Faces below equatorial plane project to bottom then are plotted on equatorial plane in a projection to the north poleshown as open symbols.
Those with vertical faces plot on circumference.
Crystals faces are plotted based on angles measured from crystals.
Easiest is to plot using two angles:
Think of as latitude and longitude on a globe, location of cities � but distribution of cities don�t have symmetry.
a) Distance along circumference � along great circle � like longitude � indicated as f - theta.
b) Distance from center � along small circle � like latitude � indicated as r - phi.
Look at plotting Ithaca on globe - f = 76�, r= 48� (90 - 42).
Plotting facilitated by use of stereographic projection.
Types of projection � for crystallography use an equal angle net � Wulff net.
In structural geology, use an equal area net - Schmidt net.
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