CREATE TABLE table_7699 ("Material" TEXT, "Formula" TEXT, "Refractive index ( es )  589.3nm" TEXT, "Hardness  (  Mohs' scale  ) " TEXT, "Density  ( g/cm 3  ) " TEXT, "State of the art" TEXT)

How much is the density with a hardness of ~ 8.3?
SELECT "Density (g/cm 3 )" FROM table_7699 WHERE "Hardness ( Mohs' scale )" = '~ 8.3'
SELECT "Density (g/cm 3 )" FROM "table_7699" WHERE "Hardness ( Mohs' scale )" = '~ 8.3'