Which of the following describes nonfoliated rocks?

Nonfoliated rocks are a specific type of metamorphic rock characterized by the absence of a layered or banded appearance. This lack of foliation typically arises when these rocks are subjected to uniform pressure and temperature conditions, rather than the directional pressures that lead to the alignment of mineral grains seen in foliated metamorphic rocks.

The correct choice highlights that nonfoliated rocks form without the significant directional pressure that would cause minerals to align. Instead, they may form from the alteration of pre-existing rocks, such as limestone transforming into marble, under conditions of high temperature and pressure where the pressure is applied uniformly.

Understanding this distinction is critical in geological studies, as the properties of nonfoliated rocks can indicate the conditions under which they formed. This contrasts with foliated rocks, which display a distinct layering due to the alignment of minerals.