Abstract: The ore from the Gaosongshu deposit in Dunhua City, Jinlin Province is diatomaceous earth of poor quality with clayey minerals and fragments. Analysis on the samples from the deposit shows that, as the chemical compositions of the wallrocks, interbeds and ores are almost same, the regular industrial indexes cannot distinguish ore from rocks. In order to evaluate the deposit accurately, we add loose dry density to the basic testing items for the samples. After repeated tests, the loose dry density ≤ 0.95 g/cm³ is determined as one of the industrial indexes, which successfully solves the problem of orebody delineation and ore quality evaluation.