Feldspar as an abrasive is used mainly in scouring soaps and window-wash.
It had every appearance of having been tampered with; sand or some other abrasive put into it.
It has an extensive use as an abrasive for grinding and polishing.
No doubt its only use was as an abrasive, after being pounded fine.
Certainly this was no place to set down the full weight of Astro nor to ...