Diamonds and sauce: crystals in terpenes.

What the diamonds are

THCA diamonds are crystalline structures of tetrahydrocannabinolic acid — the acidic precursor to THC. They form when a hydrocarbon extract is left to settle under controlled conditions: the THCA slowly crystallizes out of the solution, growing into faceted, translucent chunks. The process is called crystallization, and it's the same physical principle behind rock candy — a dissolved compound coming out of solution as crystals.

What the sauce is

As the diamonds crystallize, the liquid they leave behind concentrates everything that didn't crystallize — primarily terpenes, plus the remaining cannabinoids. That liquid is the terp sauce (or just "sauce"): viscous, aromatic, and terpene-rich.

Why they're sold together

Diamonds alone are nearly pure THCA — potent, but with most of the flavor left in the sauce. Sauce alone is flavorful but less concentrated. Jarred together, the crystals sit in the liquid they grew from, and the combination carries both. Some products separate them further; some whip them into a uniform texture (that's the road to badder).

Sugar wax, covered in the textures article, is the close cousin: smaller crystals suspended in sauce, never grown as large. Same family, different crystal size.