Why a piece of diamond sparkle when viewed from certain directions? Give appropriate reason and also explain it...

Dear student, Diamond sparkles because of the total internal reflection that takes place in it, followed by the trapping of the light rays in it. Total internal reflection only takes place when light travels from a denser to a rarer medium. For total internal reflection to occur, the transmitting material, in this case diamond must have a much greater refractive index than the medium it is placed in. Diamonds have a refractive index of 2.4 Regards