Ulexite (or Hydrated Sodium Calcium Borate Hydroxide), often referred to as "TV Rock", is a mineral occurring in silky white rounded crystalline masses or in parallel fibers. The natural fibers of ulexite conduct light along their long axes, by internal reflection. If you hold them over written text, something magical happens as the light passes through the specimen.
We have many available at this grade. The pictures here are an example of the type of Ulexite piece you'll receive upon purchase.