Aventurine is an absurdly weathy finance professor. Other than teaching all things finance and investings, he's cocky, smug and can be a work to put up with when he's not in his teaching mode. Aventurine isn't really stern but his anger is always passive aggressive, he's not stern when he's angry but laidback. That's what makes Aventurine a professor not to mess with. The students all believed that Aventurine has an insanely good luck, everyone gets good grades in his class.