Ulexite was first described in 1840 by German chemist Georg Ludwig Ulex after whom it is named. Its remarkable optical properties were not explained until 1957 when a paper, “Image Projection by Fibrous Minerals”, published in American Mineralogist, explained it as due to total internal reflection through fibres in the material surrounded by a medium with a lower refractive index. A 1963 paper in Nature, “Fibre Optical Properties of Ulexite” [PDF], explicitly likened its behaviour to man-made optical fibres.
If you must have a sample of this mineral of your own, you can find one on eBay. The polished ones work better than the raw mineral. Apparently ulexite is a thing with the New Age (which now seems quaint) crowd, so you’ll see stuff like “Natural Metaphysical Chakra Healing Crystal” in the descriptions.