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The Stone Corner

A Conversation About Marble

Student: Where does marble come from?

Teacher:  Marble comes from limestone. You could say it's a "newer" limestone.

S: What? Marble is really just a 'newer' limestone?

T: Yes. According to the Vermont Marble Company, "the original sedimentary limestones were formed in an ancient seaway, mainly from the remains of marine organisms and lime muds resulting from chemical precipitation. These original sediments consolidated, forming coherent rocks termed "limestones."

S: Oh, that's why often there are a little bit of shells, fossils and mud in some limestones.

T: That's right. 

S: Well, how did limestone become marble? 

T: "Subsequent heat, pressure and hydrothermal solutions brought on by a period of earth movements, resulted in the extensive deformation of the limestone beds and a re-crystallization that produced the highly crystalline character of commercial marble."

S: Ah ha. That's why marble is tighter grained (harder) and shinier.

T: Yes. Basically, marble is a metamorphic rock resulting from recrystallization of limestone.

S: You mean marble is a newer limestone.

T: (Sigh.) Yes.

Geology: Limestone to Marble

The Geology of Sculpting Stone Series

Click to Download:

Pacific Northwest Granite  

Columbia River Basalt 

Indiana Limestone

The above series is designed to explore one key aspect of stone sculpture that is unique to the art form, its geology.

Why should you care about the geology of stone?

In a rapidly changing and competitive art world, stone sculpture is one of the few arts that can tie back to the beginning of art and is of a of medium unlike any other.  Knowing more about the geology of the stone will allow stone sculptors to:

  • Select stone that has a compelling history for the sculptor and audience alike
  • Marvel at its various elements of grain, color and texture as it is worked
  • Consider how the chosen artistic form relates to the science of the stone
  • Weave into the final art work story a geologic component that enhances the interest in the work by the potential buyers

Each of the presentations covered a commonly worked stone by NWSSA members and follows a structured outline:

  • The Stone Defined
    • General Description, Physical/Chemical Properties and Historic Use
    • Specimens (macro and thin section)
    • Specific Occurrences
  • Geology
    • Age and Geologic Description
    • Formation Environment and Processes
    • Global Paleogeographic Setting
    • Modern Analogs
  • Select Creations
    • Art
    • Architecture

I hope you enjoy these presentations and please use them to enliven your art.

Michael E. Yeaman

YeamanSignature

The Stone Column Jade

The Stone Column
Jade
by Bill Laprad
by Bill Laprade


Ed. Note: The Stone of Heaven is one of the most revered natural substances in the world, such has been the case for centuries, particularly in Asia. What other mineral would make a Chinese emperor offer fifteen cities for a jade carving that he could hold in the palm of his hand or make Montezuma smile when he heard that the Spaniard Cortez was interested only in gold, since Montezuma's most precious possession was jade. 

Since Neolithic times, no other mineral has been so venerated, nor so often intertwined with the dead to accompany them into the afterlife. In this life, to the Chinese, jade embodies the five cardinal virtues of life: charity, modesty, courage, justice, and wisdom. But China and Asia have not had a monopoly on jade; jade art and tools have been found in the Maori, Olmec, Aztec, and Mayan cultures, and among the NW American Coast Indians and Eskimos.

The English word jade has a circuitous derivation. It started with the Spanish expression "piedra de hijada", meaning the "stone of the loins", because it was claimed that this stone could cure diseases of the kidneys. This gave rise to the word nephrite, from the Greek word for kidneys: nephros. The French equivalent l'ejade eventually evolved into le jade, and its English translation, jade. 

Physical Traits
Jade is actually two minerals: nephrite and jadeite.

Read more ...

How To: Finishing Soft Stone

 JoAnne Duby

Here we share the experience and knowledge of those who have found their own answers to some of the inevitable and sometimes nagging questions forever popping up in our sculpture projects. Newcomers will find it useful and even those who have been carving for some time can never deny the benefit of a tune-up.

FINISHING SOFT STONE  
By JoAnne Duby

Soapstone, Chlorite, alabaster, limestone, Pyrophyllite
I break the carving down into four stages:

• Clean-up, if it is a rough boulder stone.
• Rough out of design.
• Completion of the design, sanding up to 220 grit.
• With silicone carbide paper, sanding up to 320 grit, and then polishing up to 3000 grit. Wax it if desired or if it's going outdoors.

I find you can really move lines around till you get to 320 grit. To get a great finish on soft stone I very rarely use diamonds they are just too aggressive for soft stone. It's like taking a machine gun to a knife fight......way over-kill.

Read more ...

The Stone Column: Alabaster - July/Aug 1996

Waxy, multi-colored alabaster has been the choice of stone for artists and artisans for millennia. It not only serves as the source of beautiful sculptures, but historically it provided utilitarian objects such as jars and casks. It was prized by the Assyrians and the Egyptians for its beauty. One of its most handsome and unique characteristics is its ability to pass light; imagine, a stone that can transmit light through it. While we sculptors use it for carving, alabaster's cousin, gypsum, is around us most everywhere we go and is handy on all of our workshop shelves.

Geology

Alabaster is one of several forms of gypsum, and it is both a mineral and a sedimentary rock. It is a hydrated calcium sulfate, Ca S04' 2 H20 that is found in many places throughout the world. It is a sedimentary evaporite deposit that precipitates from the evaporation of saline water. The ideal conditions for its formation are (I) a restricted arm of the sea, (2) intense evaporation, (3) replenishment by normal sea water and (4) gradual sinking of the basin.

Read more ...