chemical rock formed by crystallization
of excess dissolved minerals

Chemical sedimentary rocks.

Explanation: Those may be a type of sedimentary rocks called "chemical sedimentary rocks". This type of rock forms when mineral constituents in solution become supersaturated and inorganically precipitate.  Formed by deposit of dissolved substances, were the largest volume corresponds to masses of salts accumulated by supersaturation of seawater. When seawater is stagnant, it begins to evaporate and dissolved minerals precipitate, this process gives rise to evaporites, for example gypsum and gem salt.

the answer is ampere

the ampere is used to measure electricity. an ampere is a unit of electric current equal. a unit of measure for the flow of current in a circuit. one ampere is the amount of current flow provided when one volt of electrical pressure is applied against one ohm of resistance.