Abstract: Crystalline ceramic particles including at least 90 percent by weight Al2O3, based on the total weight of the crystalline ceramic particle, and having a density in a range from 50 to 75 percent of theoretical density, a long term flow conductivity of at least 4.5×10?12 m2-m at 55.2 MPa, and a smallest dimension of at least 100 micrometers. The crystalline ceramic particles described herein are useful for example, as proppants, insulation (thermal and/or sound), and filler.