Old Moss the mole digs up rough stones. You buy, cut, polish and sell them before the market closes.
Turn the stone FRONT, SIDE and TOP. Flaws only show from some angles. Then bid: Moss may say no.
Drag a cut across the stone to slice the flawed side off, pick a pattern, tap CUT. Less weight can still sell for more.
Rub each zone to polish it to 100%. Rub too long and it chips.
Sell to the buyer who loves that gem. Three sales under cost close the stall.