Some elements, when mixed together can be separated from one another, but it doesn't always happen.
For example, if you thoroughly mix the solute oil and the solvent water, breaking the liquids into small globules, the mixture will soon separate. Oil and water do not mix on a permanent basis.
Note that you could also mix the water in some oil. In that case, the water would be considered the solute and the oil the solvent.
Smoke is an example of solid particles mixed in a gas. The solute smoke particles are added to the solvent air and mixed by convection currents.
After a while, the particles will settle to the ground. Solid particles in the air are a major part of air pollution.
Muddy water is an example of solid particles mixed in a liquid. Dirt is added to the water and made into a mixture by stirring the ingredients. After a while, gravity will cause the particles to settle to the bottom.
Blood is another example of solid particles in a liquid. The blood cells can be separated with a centrifuge.
In many cases, the difference in weight of the substances will allow the effect of gravity to separate them.
A centrifuge will accelerate the effect of gravity by using centrifugal force to separate the materials. It is possible to separate the milk and cream particles (or cream globules) by spinning the liquid in a centrifuge. Hospitals use the centrifuge to separate blood cells from the plasma, which can be preserved longer.
Changing a liquid into a gas can often separate liquid mixtures. This can be done by natural evaporation or by boiling the liquid mixture. This is often done in separating salt-water solutions.