Among the unique stones available, Porphyry can only be quarried in a limited number of places. It’s a material that has been known and used since ancient times. Important relics and monuments in porphyry have been discovered at Assyrian-Babylonian, Egyptian and Roman sites, the cradles of civilization.

Quarried  since the time of the Romans, porphyry became one of the most important varieties of stone in Europe. The rock, formed under such intense heat and pressure that it is more dense than granite, was ideal for paving all those Roman roads, including the ones that traversed the Alps and became the pavements of Paris.

Because of its density, porphyry absorbs almost no water at all. That makes it impervious to cracking -- water can't get in to freeze and expand. That trait is useful, not only in the Alps but also where changing seasons create multiple freeze-thaw cycles every year.

And because it doesn't absorb water, the stone dries off quickly, which makes it ideal for use in wet areas such as showers and pool decks. It is naturally slip-resistant -- the material meets requirements set by the Americans With Disabilities Act on that score, according to suppliers -- which is also a plus. Moreover, because it's incredibly hard, it resists scratches and damage from chemicals.

It is further distinguished by the richness of its coloration -- porphyry means purple in Greek -- and its characteristic purplish-red or greenish-brown swirled patterns have made it a popular choice over centuries as a building material indoors as well as out.