What crystals can I grow at home that are triply birefringent?

Answer 1

If you mean biaxially birefringent, how about borax and epsom salts?

http://en.wikipedia.org/wiki/Birefringence


Note that growing single crystals large enough for amateur use take some care and effort. Here is a site telling grad students how to do it:

http://www.xray.ncsu.edu/GrowXtal.html


Here is a site that confirms feasibility of growing alum and borax, but they go for many small crystals as opposed to large ones.
http://bizarrelabs.com/crys.htm

Here's a general site on crystal growing at home. But instead of putting it in the Sun, you will want to put in an environment where the temperature is more constant.

http://www.geocities.com/crystalgrowing2001/index.htm

Good luck.