Although copper is the third most  abundant trace mineral in the body (behind iron and zinc), the  total amount of copper in your body is only 75-100 milligrams, less  than the amount of copper in a penny.
Gratuitous. Bestowed or granted without consideration or exchange for something of value. The term gratuitous is applied to deeds, bailments, and other contractual agreements. A gratuity is something given by someone who has no obligation to give and can be used in reference to a bribe or tip. gratuitous. adj. or adv. voluntary or free. gratuitous
Leaving some money on a restaurant table is a common way of giving a tip to the serving staff. A gratuity (also called a tip) is a sum of money customarily tendered, in addition to the basic price, to certain service sector workers for a service performed or anticipated. Depending on the country or location, it may be customary to tip servers in bars and restaurants, taxi drivers, hair stylists, and so on.