Paint it, Gold leaf it, verdigris it, weather it!
All of my fireplaces are made of pre-cast cement
and all of them have been painted with water-based acrylic paints.
I painted our very large Hall fireplace to look as if it were made of stone
I added gold leafing to the shell and painted the cement to mimic marble for our upstairs bedroom fireplace.
Dust off the dirt and start painting. No primer necessary
This urn has been out in our harsh weather for more than 17 years...no sign of peeling or fading
Even synthetic stucco can be painted with acrylic paints
I need to finish the door surround
The upper part (Trumeau) of our living room fireplace
also made of pre-cast cement pieces and painted with water-based paints. A sealer (Okon) is a good idea for the hearth so you can clean it now and then
A cement garden urn painted
If you can wait a few years, nature is the best Artificer of them all
A little paint and a little help from the weather is all it takes.