A mouthful of diamonds may be referring to two things: It may be a reference to a method mine workers in Africa use to steal diamonds. As seabed gravel is churned up, mine workers put diamonds underneath their fingernails and later into their mouths when no guards are watching. This is an eloquent way to call out someone for being unfaithful. Referring to the drug use mentioned in the first verse, diamonds might be interpreted as slang for MDMA. This name arises due to the fact that many MDMA pills are pressed into the shape of a diamond. Nevertheless, the allusion highlights how her partner is deceiving her (about drug use and/or infidelity). Her sultry words talk about a pattern that she’s uncovered in her lover’s behavior–a parallel to the pattern used by mine-workers or a parallel to a pattern of someone addicted to ecstasy. Read more on Last.fm.