Diamonds and sauce is a concentrate made of two parts. The diamonds are crystals of nearly pure THCA, and the sauce is a thick, terpene-rich liquid that the crystals sit in. Together they give you both strength and flavor.
To make it, extractors usually start with a hydrocarbon extract, often a live resin from fresh-frozen plants, and let it sit under controlled conditions for days or weeks. THCA slowly crystallizes and settles out, forming the diamonds, while the terpenes and other compounds separate into the sauce.
The diamonds by themselves are very potent once heated, since THCA turns into THC. On their own they have little flavor because they are so pure. The sauce brings the aroma. Many people dab a small diamond with a bit of sauce for a balance of both.
Diamonds and sauce are usually dabbed, sometimes at lower temperatures to keep the terpene flavor. They are also used in some infused pre-rolls. Start with a small amount; this is one of the strongest products on most menus.
Store it cool and sealed. Over time the sauce and diamonds can continue to separate. Check the COA for potency and solvent results.