A method for making crystalline (±)-Δ 9 -tetrahydrocannabinol comprising: allowing trans-(-)-Δ 9 -tetrahydrocannabinol and trans-(+)-Δ 9 -tetrahydrocannabinol to crystallize from a first composition comprising trans-(-)-Δ 9 -tetrahydrocannabinol, trans-(+)-Δ 9 -tetrahydrocannabinol, and a non-polar organic solvent to provide crystalline (±)-Δ 9 -tetrahydrocannabinol, wherein the first composition was obtained by: converting (-)-p-menth-2,8-dien-1-ol to trans-(+)-Δ 9 -tetrahydrocannabinol by (i) stirring a mixture of olivetol, zinc chloride and anhydrous dichloromethane at 40°C for one hour, adding a solution of the (-)-p-menth-2,8-dien-1-ol and anhydrous dichloromethane drop-wise over 1 hour at 40°C to the stirred olivetol-containing mixture, and stirring the resulting mixture for an additional 40 minutes at 40°C, (ii) cooling the mixture to -10°C, adding a solution of BF 3 ·Et 2 O in anhydrous dichloromethane drop-wise over 1 hour at -10°C, and stirring the mixture for 30 minutes at -10°C, and (iii) adding cold water, stirring the resultant biphasic mixture for 20 minutes at 0°C, and isolating the crude trans-(+)-Δ 9 -tetrahydrocannabinol from the organic phase; forming a biphasic composition comprising (i) a first organic phase, and (ii) an alcoholic-caustic phase containing the crude trans-(+)-Δ 9 -tetrahydrocannabinol resulting from step and trans-(-)-Δ 9 -tetrahydrocannabinol; separating the Δ 9 -tetrahydrocannabinol from the resulting phase containing the Δ 9 -tetrahydrocannabinol; and contacting the Δ 9 -tetrahydrocannabinol from step with a non-polar organic solvent to form the first composition. allowing trans-(-)-Δ 9 -tetrahydrocannabinol and trans-(+)-Δ 9 -tetrahydrocannabinol to crystallize from a first composition comprising trans-(-)-Δ 9 -tetrahydrocannabinol, trans-(+)-Δ 9 -tetrahydrocannabinol, and a non-polar organic solvent to provide crystalline (±)-Δ 9 -tetrahydrocannabinol, wherein the first composition was obtained by: converting (-)-p-menth-2,8-dien-1-ol to trans-(+)-Δ 9 -tetrahydrocannabinol by (i) stirring a mixture of olivetol, zinc chloride and anhydrous dichloromethane at 40°C for one hour, adding a solution of the (-)-p-menth-2,8-dien-1-ol and anhydrous dichloromethane drop-wise over 1 hour at 40°C to the stirred olivetol-containing mixture, and stirring the resulting mixture for an additional 40 minutes at 40°C, (ii) cooling the mixture to -10°C, adding a solution of BF 3 ·Et 2 O in anhydrous dichloromethane drop-wise over 1 hour at -10°C, and stirring the mixture for 30 minutes at -10°C, and (iii) adding cold water, stirring the resultant biphasic mixture for 20 minutes at 0°C, and isolating the crude trans-(+)-Δ 9 -tetrahydrocannabinol from the organic phase; forming a biphasic composition comprising (i) a first organic phase, and (ii) an alcoholic-caustic phase containing the crude trans-(+)-Δ 9 -tetrahydrocannabinol resulting from step and trans-(-)-Δ 9 -tetrahydrocannabinol; separating the Δ 9 -tetrahydrocannabinol from the resulting phase containing the Δ 9 -tetrahydrocannabinol; and contacting the Δ 9 -tetrahydrocannabinol from step with a non-polar organic solvent to form the first composition. converting (-)-p-menth-2,8-dien-1-ol to trans-(+)-Δ 9 -tetrahydrocannabinol by (i) stirring a mixture of olivetol, zinc chloride and anhydrous dichloromethane at 40°C for one hour, adding a solution of the (-)-p-menth-2,8-dien-1-ol and anhydrous dichloromethane drop-wise over 1 hour at 40°C to the stirred olivetol-containing mixture, and stirring the resulting mixture for an additional 40 minutes at 40°C, (ii) cooling the mixture to -10°C, adding a solution of BF 3 ·Et 2 O in anhydrous dichloromethane drop-wise over 1 hour at -10°C, and stirring the mixture for 30 minutes at -10°C, and (iii) adding cold water, stirring the resultant biphasic mixture for 20 minutes at 0°C, and isolating the crude trans-(+)-Δ 9 -tetrahydrocannabinol from the organic phase; (i) stirring a mixture of olivetol, zinc chloride and anhydrous dichloromethane at 40°C for one hour, adding a solution of the (-)-p-menth-2,8-dien-1-ol and anhydrous dichloromethane drop-wise over 1 hour at 40°C to the stirred olivetol-containing mixture, and stirring the resulting mixture for an additional 40 minutes at 40°C, (ii) cooling the mixture to -10°C, adding a solution of BF 3 ·Et 2 O in anhydrous dichloromethane drop-wise over 1 hour at -10°C, and stirring the mixture for 30 minutes at -10°C, and (iii) adding cold water, stirring the resultant biphasic mixture for 20 minutes at 0°C, and isolating the crude trans-(+)-Δ 9 -tetrahydrocannabinol from the organic phase; forming a biphasic composition comprising (i) a first organic phase, and (ii) an alcoholic-caustic phase containing the crude trans-(+)-Δ 9 -tetrahydrocannabinol resulting from step and trans-(-)-Δ 9 -tetrahydrocannabinol; separating the Δ 9 -tetrahydrocannabinol from the resulting phase containing the Δ 9 -tetrahydrocannabinol; and contacting the Δ 9 -tetrahydrocannabinol from step with a non-polar organic solvent to form the first composition.