For the second quarter in a row, U.S. Silica Holdings (NYSE: SLCA) reported a large uptick in frack sand sales. Also, for the second quarter in a row, those increased sales didn’t translate into a positive earnings per share result. For investors that have watched oil and gas activity pick back up again and see demand for frack sand rise even faster, it might seem a little concerning that U.S. Silica can’t make a profit.