What are the essential elements of possession of a controlled substance?

"The essential elements of possession of a controlled substance are `dominion and control of the substance in a quantity usable for consumption or sale, with knowledge of its presence and of its restricted dangerous drug character. Each of these elements may be established circumstantially.' [Citations.]" (People v. Palaschak (1995) 9 Cal.4th 1236, 1242.) "[T]he nature of a substance, like any other fact in a criminal case, may be proved by circumstantial evidence. [Citations.] It may be proved, for example, by evidence that the substance was a part of a larger quantity which was chemically analyzed [citations], by the expert opinion of the arresting officer [citation], and by the conduct of the defendant indicating consciousness of guilt. [Citation.]" (People v. Sonleitner (1986) 183 Cal.App.3d 364, 369, italics added.)