What mixture has no uniform composition and exist in two or more phases?

A heterogeneous mixture is a mixture in which the composition is not uniform throughout the mixture. A phase is a separate layer in a heterogeneous mixture.
A heterogeneous mixture is a mixture in which the composition is not uniform throughout the mixture.A phase is a separate layer in a heterogeneous mixture.
Homogeneous and heterogeneous mixtures
However, a heterogeneous mixture has non-uniform composition and its constituent substances are easily distinguishable from one another (often, but not always, in different phases).