I suppose since it forms in solution and by chemical reaction, that the formation is random and dependent on conditions. For instance some forms in stalactites from limestone interacting with copper in solution. Others form around copper deposits on the ground that interact with catbonated water. I suppose you get a layer of water which interacts with the copper, the result is malachite. If this process occurs over and over you might get a layered appearance.
Malachite is a secondary mineral of copper, which means it is formed when copper minerals are altered by other chemicals. It occurs when carbonated water interacts with copper minerals, or when a solution of copper interacts with limestone. Malachite is opaque and always green.