THC diamonds aka THC crystalline are 99% pure THC-A. Their size is small and can resemble granulated sugar and at largest full-sized diamond look-alike that are a few millimeters wide. The remaining 1% of THC diamond is made up of terpenes and other cannabinoids. This is THC in its purest form possible.
What is THC-A?
THC-A is an inactivated cannabinoid. THC-A will convert into THC after it has been heated to extreme temperatures but is utterly ineffective on its own and will not produce the same psychoactive and euphoric sensations you would expect from a product high in THC.