Final answer:
Hydrothermal rocks, precipitated from hot water, are sometimes considered a type of metamorphic rock, which is formed by the alteration of pre-existing rocks under heat, pressure, or chemical influence.
Step-by-step explanation:
The rocks formed directly by precipitates from hot water are often called hydrothermal rocks. However, some geologists consider these to be a specific type of metamorphic rock. Metamorphic rocks are characterized by the transformation of pre-existing rocks through the processes of high temperature, high pressure, or the action of chemically reactive fluids.
This alteration, known as metamorphism, may result in recrystallization of minerals, a change in rock composition, or the development of a textured orientation in the minerals, such as foliation. The term protolith is used for the original rock before it underwent metamorphism. Examples of metamorphic rocks include schist, slate, marble, and quartzite, which were formed from pre-existing rocks such as shale, limestone, or sandstone.