Calci-Sand is not a 'natural' sand. It is a man-made substance that clumps & hardens when it gets wet (i.e. in your beardie's tummy)
I have had calci-sand in the past for my hermit crabs... I took some and wet it and that was a few years ago and I still have the hardened chunk in the storage closet upstairs. Someone on here used Calci-Sand to fill a hole in concrete outside... and the hardened calci-sand survived a storm or hurricane or something (forgot the exact story but something like that)
That is definitely not something we want in our beloved pet's belly!
PlaySand- which is sterilized/cleaned/sifted beach sand- is natural sand and the only sand that is OK to use... though it still can cause impaction if they swallow too much of it (which is why it's more recommended for adult beardies since they lick their surroundings less.)
Also... whats in nature is not always best. Beardies don't live neary as long and healthy in the wild as they do in the right captive settings. That goes with most animals. When we keep animals in captivity as pets (or in zoos, etc.) we pamper them and exclude the dangers of nature in their lives