Imagine if an artist could take millions of years to complete a single painting.
Over millions of years the natural process of water penetrating and seeping into stones, bringing with it solutions of iron and magnesium, along with other elements, leaves traces of color and forms within the stone. This, along with cracks created from pressure and channels of water, combine their lines to push up imagery of mountains and trees, creating landscapes of unmeasurable beauty.
Known under a few names, such as: scenic stone, pictorial stones, pietra paesina, marble ruiniforme, lithographic limestone, and stone Florence (there may be others too), these stones were highly prized in early modern Europe and, before that, Asia, because of the beautiful naturally created organic landscapes.
There are three areas in particular that are known (or were known at some point in time) for these types of stones: Florence, Italy; Jasper, Oregon; and Cotham, England.
Artists also used these stones as a canvas adding their own hand and transforming the natural lines and shapes of the stone's face with their own paints, like the one on top painted by Dutch painter Hercules Segers, and the other one by Johann König.
Books about this topic mentioned on source sites:
Aberrations by Jurgis Baltrusaitis
"Album of Rain Flower Pebbles Treasure"
Jiangsu Ancient Book Publishing House (HK) (1989)