I experimented and found a great formula for achieving a faux-stone finish on the fireplace! It's so simple and takes just two simple ingredients.

First start with flat paint in the color of your choice. I measured out 1/4 cup into a mixing tray. I then added 1/4 cup of Plaster of Paris, little by little, stirring it in until smooth. Equal parts paint and PoP gave a great consistency for this! Plaster of Paris is readily available in the paint section at hardware stores. I worked with small batches as the plaster will set fairly quickly.

I applied it using a 6" putty knife, smoothing seams as I went, going in different directions, creating flowy movement. One it started to set, I went back through with a clean putty knife and started dragging the setting plaster (using varying pressure on the putty knife) to create textured effects.