After teaching optical mineralogy using these models (left & right), I felt the need for better ones. We did not have any uniaxial models, and the biaxial ones were falling apart, and too fragile to let students handle.
The four designs are provided below in PDF format. Note that some aspects of the design were not actually implemented, speciically, the "rods" of coordinating colors to show the wave normals (and, in some cases, ray paths). These may yet be inked on, or otherwise added to the models.
The models are made of 1/4" colored acrylic sheets. This makes them very strong, and the joints are extremely well bonded. The cost for the four models was about $300, but this is only for materials - labor is free in our campus shop.
Here are the models: note that all circular sections are colored red (well, reddish, anyway), and that other principal sections are differently colored. If you were to make some planes clear acrylic, the cost would decrease substantially.
There was only one glitch - making the circular sections so that they actually formed circles turned out to be a little tricky, and so the biaxial positive model has a small error. If you use these plans, be sure to warn your fabricator. The problem came late in the process, and the "glue" in these materials cannot be dissolved to fix the problem.
|Biaxial Positive||Biaxial Negative|
|Bi. Pos. Close-up||Bi. Neg. Close-up|
-Dave Hirsch, 3/10/03