Well, It doesn't look like an stone (The painting) because it's blurred . There's to many AA Pixels withdrawing the focus of what is really the color.
To achieve best results you have to do the reverse of AA: the contrast,
Stones has contrast between the surfaces, see in the image.
You have to first focus on defining surfaces with contrast and then add the texture on each surface.
This image doesn't have texture, as you can see, but it's interesting because it breaks down the ability of doing stones at two points, surfaces (the one which is shown) and texture.