Agarwood is not a species of tree so much as a condition: when an Aquilaria tree is wounded, it can deposit a dark, aromatic resin into the wood around the injury, and the result is far denser than the surrounding timber. Beads cut from heavily resinated wood sink in water; that is what "sinking grade" means.
One thing to state plainly: several Aquilaria species are listed under CITES, and wild-collected material is restricted. Our stock is plantation-grown — planted, wounded and harvested deliberately — which is both legal and more consistent in quality. The scent is faint when cold and comes out with warmth and handling.