Answered By: Joelle Maurepas Last Updated: Sep 29, 2015 Views: 66
This is a little outside of our ability to explain. A couple of guesses hazarded have been (1) that the shapes you are seeing are pareidolia (A phenomenon in which our brains interprets symbols and superimpose patterns upon randomness) (2) that the triangles are there but that the triangles arose via pure chance (3) that they derive from some kind of imperfection in the inner surface of the hourglass (4) or that the minerals used to make the sand happen to bond and cleave in that pattern. Or a mixture of all four.
My personal opinion is that either your (1) sand has moisture that causes it to bond and slough of in a orderly fashion or (2) that it's been subjected to some form of more or less uniform vibration like this sand in the attached video.
In that video, the material used is sand. However, if you look up videos of substances known as ferrofluids that are subjected to standing sound and electro-magnetic waves, you will observe them formed shockingly precise and strange geometric shapes.
But in short, we cannot tell you for certain exactly what it is that the image you sent to us depicts.
You might find a better and more informed opinion by contacting LSU's geology department here, as mineral and mineral-derived materials' behavior is a specialty of theirs:
Department of Geology & Geophysics
College of Science
Louisiana State University