Marble is a natural stone of considerable beauty, the choice of sculptors throughout the ages.

Marble and onyx are, analytically speaking, composed mainly of crystalline calcium carbonate. Admixtures of other minerals give a broad range of colors, types, and features.

Marble was deposited on the ocean floors of long-ago. Mainly it consisted of the shells of unimaginably numerous organisms leaving behind the permanent part of themselves to turn to stone and build up in accumulations often miles deep, later overlain by more miles of other rock. Such immense weight, acting along with great heat over a very lengthy time, compressed and altered it to the dense smooth structure of marble.

Onyx was , instead, deposited under blue sky by bubbly hot springs rising from deep within the earth. What was laid down was mostly caliches, sometimes wormy travertine, and very rarely the fine crystalline treasure of onyx. It is a kind of marble but translucent; it takes in light, and gives it back in a subtle glow.

Supplies of marble, waiting to be used and so become art, are inexhaustible. Along with limestone, they are so abundant that they are one of the basic building blocks of the continents, and with their captured carbon they're one factor in the age-old process of release and take-up of carbon, in the surface chemistry of our planet. Which is beside the point. There's lots of it.

Marble is extremely permanent. It's been available pretty much forever, and with minimal care will last forever. It is tangible. It has a constancy not found in paintings, fabrics, and literature and talk, and this very stability and permanence give it a character of enduring value.