Space Stones were naturally silver in color, and completely weightless. They were also invisible to one's spiritual sense as a person's spiritual sense registered it as regular space instead of a natural object.
Space stones were very difficult to find. Most Space stones that were around were tiny ones, no larger than the a grain of rice. Even at that size, they held a lot of stone.
Alex didn't know how, but he knew that people could turn those Space stones into usable artifacts like rings or necklace, which could then hold a lot of items within it.
While a Space Stone did hold a lot of natural space within it, it couldn't be used before it was refined into an artifact. Afterward, however, depending on the quality of the refinement process, only part of it could be used.
