These substances are all minerals, with the exception of Hu Po (amber). Their “heavy” quality can be thought of through the doctrine of signatures as conferring an anchoring effect on the Shen. In the case of amber, although it’s not a mineral (instead, old, hardened sap), its qualities of being old and very slow to form perhaps contribute to a similar quality.
These herbs are all somewhat difficult to digest and are minimally soluble in water. For this reason, it doesn’t exactly make sense to purchase them as granules. They are as potent as they can get in their raw form. Unlike a plant herb, where something can be extracted and potentiated, a decoction or granule is going to be much, much weaker than the raw substance. It’s like taking a 1 gram calcium tablet, boiling it in water, straining the liquid, and dumping out the calcium powder that’s at the bottom of the pan. How much do you think made it into the water? Just a fraction of what was in the pill. The only possible advantage to using any of these herbs as granules might be that they’re easier to digest than the raw powder, but this is only because they’re mostly starch and very little mineral. For much less money, you could have just used the raw powdered medicinal at a dose of something like 10-20% of what you would have used in granule form (you’ll have to figure out the actual math on this).