Microphotographs for Research in Ceramic Petrography, by David Glen Robinson

Dr. David Robinson is a visiting researcher at TARL. This article is part of TARL’s September 2017 newsletter.

Work at TARL’s microscopy lab in 2017 has focused on Caddo sites, particularly the George C. Davis site (41CE19). Imagery in
the microscope has been captured for sharing with scholars with an interest in ceramics and Caddo culture. Digital
photography with a dedicated computer setup (although still a part of the TARL-UT network) makes capturing, sharing, and
distributing the imagery easy. The hard part is still identifying unknown minerals in thin section and centering them in front
of the camera’s shutter.

The assistance of Marilyn Shoberg in operating the digital system is gratefully acknowledged.

All thin section images in this article are from the George C. Davis Site (41CE19).


Feldspar particle in Paste Group E. Feldspar is a telltale sign of nonlocal wares at the George C. Davis site.

Paste Group C. This paste group is an unusual hematite-tempered group. The small brown (medium silt-sized) particles may be hematite. The actual hematite temper particles are coarse sand-sized (not visible in this view).

Grog temper particle. Note color difference, high angularity, and much smaller interior particles in the grog particle.

Large mass of bone tempering. Bone material almost fills the image. Bone particles may take almost any shape.

Ilmenite is titanium oxide; it appears as a fractured mass with white speckles, which are small masses of elemental titanium. It could
well be a specific telltale sign in Caddo country, but research has not yet determined this.

Bug eggs in blue void. Invertebrates lay eggs in ceramic voids. Sometimes they are preserved by carbonization in the ceramic firing. Species unknown.

Void with woody burnout. Some sections from George C. Davis have up to 2.5% of such voids. Note the black interior particle and jagged
or feathery black interior rim of the void. The void was originally filled with a woody organic material, and firing burned out all
the material around the interior rim.

Hex void. Some sections from George C. Davis have numerous voids of irregular hexagonal shapes. Many are more elongated than this one. Some interpretations speculate that these are the shapes left by seeds being added to the ceramic paste. The material burns out, leaving the hexagonal shape. Black masses inside the void may be remnant material.

Special thanks to the Texas Historical Commission for their funding of this project, and to Tim Perttula (PI).

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