A powdered composite filtration medium comprising: composite particles, each composite particle including at least one diatomite particle and at least one expanded perlite particle sintered together, the powdered composite filtration medium including less than 0.1 wt% total crystalline silica and having a permeability of at least 0.25 darcy, wherein the composite particles are obtainable by: 1) calcining a feed blend of 75 wt% or less diatomite at a temperature of about 982°C or lower; 2) calcining a feed blend of 75 wt% or less diatomite with 5 wt% or less soda ash at a temperature of 871°C or lower; 3) calcining a feed blend of 50 wt% or less diatomite with 7 wt% or less soda ash at a temperature of 704°C or lower; 4) calcining a feed blend of 25 wt% or less diatomite with 7 wt% or less soda ash at a temperature of 760°C or lower; 5) calcining a feed blend of 50 wt% or less diatomite with 5 wt% or less potassium carbonate at a temperature of 816°C or lower; 6) calcining a feed blend of 50 wt% or less diatomite with 6.8 wt% potassium silicate at a temperature of 816°C or lower; or 7) calcining a feed blend of 50 wt% or less diatomite with 5.6 wt% or less borax at a temperature of 816°C or lower, wherein the wt.% of diatomite in 1)-7) is the weight percent of diatomite in the feed blend of diatomite and expanded perlite, excluding fluxing agent, if any. composite particles, each composite particle including at least one diatomite particle and at least one expanded perlite particle sintered together, the powdered composite filtration medium including less than 0.1 wt% total crystalline silica and having a permeability of at least 0.25 darcy, wherein the composite particles are obtainable by: 1) calcining a feed blend of 75 wt% or less diatomite at a temperature of about 982°C or lower; 2) calcining a feed blend of 75 wt% or less diatomite with 5 wt% or less soda ash at a temperature of 871°C or lower; 3) calcining a feed blend of 50 wt% or less diatomite with 7 wt% or less soda ash at a temperature of 704°C or lower; 4) calcining a feed blend of 25 wt% or less diatomite with 7 wt% or less soda ash at a temperature of 760°C or lower; 5) calcining a feed blend of 50 wt% or less diatomite with 5 wt% or less potassium carbonate at a temperature of 816°C or lower; 6) calcining a feed blend of 50 wt% or less diatomite with 6.8 wt% potassium silicate at a temperature of 816°C or lower; or 7) calcining a feed blend of 50 wt% or less diatomite with 5.6 wt% or less borax at a temperature of 816°C or lower, wherein the wt.% of diatomite in 1)-7) is the weight percent of diatomite in the feed blend of diatomite and expanded perlite, excluding fluxing agent, if any. 1) calcining a feed blend of 75 wt% or less diatomite at a temperature of about 982°C or lower; 2) calcining a feed blend of 75 wt% or less diatomite with 5 wt% or less soda ash at a temperature of 871°C or lower; 3) calcining a feed blend of 50 wt% or less diatomite with 7 wt% or less soda ash at a temperature of 704°C or lower; 4) calcining a feed blend of 25 wt% or less diatomite with 7 wt% or less soda ash at a temperature of 760°C or lower; 5) calcining a feed blend of 50 wt% or less diatomite with 5 wt% or less potassium carbonate at a temperature of 816°C or lower; 6) calcining a feed blend of 50 wt% or less diatomite with 6.8 wt% potassium silicate at a temperature of 816°C or lower; or 7) calcining a feed blend of 50 wt% or less diatomite with 5.6 wt% or less borax at a temperature of 816°C or lower,