Carmichael’s Concise Review


Coming Events 2018


Semiconductor Interfaces (PCSI-45) January 14–18, 2018 Kona, HI


https://pcsi2018.avs.org


Biophysical Society February 17–21, 2018 San Francisco, CA


www.biophysics.org/Meetings/AnnualMeeting/Future/ tabid/495/Default.aspx


PITTCON 2018


February 26–March 1, 2018 Orlando, FL https://pittcon.org


255th ACS National Meeting March 18–22, 2018 New Orleans, LA


www.acs.org/content/acs/en/meetings/nationalmeetings/ meetings.html


2018 MRS Spring Meeting April 2–6, 2018 Phoenix, AZ


www.mrs.org/spring2018


American Society for Investigative Pathology


April 18–22, 2018 San Diego, CA


www.asip.org/meetings/EB_future.cfm


Histochemistry 2018 April 21–25, 2018 San Diego, CA


http://histochemicalsociety.org/Meetings-and-Courses/ Histochemistry-2018.aspx


Atom Probe Tomography and Microscopy June 10–15, 2018 Gaithersburg, MD


www.nist.gov/news-events/events/2018/06/ atom-probe-tomography-and-microscopy-2018-aptm-2018


Microscopy & Microanalysis 2018 August 5–9, 2018


Baltimore, MD www.microscopy.org 2019


Microscopy & Microanalysis 2019 August 4–8, 2019


Portland, OR www.microscopy.org 2020


Microscopy & Microanalysis 2020 August 2–6, 2020


Milwaukee, WI www.microscopy.org 2021


Microscopy & Microanalysis 2021 August 1–5, 2021


Pittsburgh, PA www.microscopy.org 2022


Microscopy & Microanalysis 2022 July 31–August 4, 2022


Portland, OR www.microscopy.org


More Meetings and Courses Check the complete calendar near the back of this magazine.


8


Figure 1 : Thin-section photomicrographs of petrographic fabric groups and specifi c features detected within ceramic artefacts. A) Sand-tempered terracotta warrior statue; B) sand-tempered terracotta acrobat fragments; C) sand-and-plant-tempered core sample from bronze waterfowl; D) untempered silty brick sample; E) dark clay-rich plastic inclusion that may indicate intentional clay mixing; F) light-colored plastic inclusions in sample that may indicate the intentional mixing with the material in the previous image; G) granite rock fragment within sand temper; H) phyllite metamorphic rock fragment within sand temper. Image width = 0.5 mm, except G and H where the width = 0.25 mm. Images taken under crossed polars, except C and F, which were taken in polarized light.


doi: 10.1017/S1551929517001237 2018 January


In spite of decades of research into the Terracotta Army of the First Emperor of China, many questions remain about how, where, and by whom these famous sculptures were made. Recently Patrick Quinn, Shangxin Zhang, Yin Xia, and Xiuzhen Li compared the results of microscopic analyses of the larger than life-sized clay statues and other ceramic artefacts recovered from the mausoleum [ 1 ]. All ceramic specimens were prepared as 30 μ m sections and were analyzed by transmission polarized microscopy with magnifi cations up to 400×. Petrographic analysis focused on the nature of particulate inclusions, clay matrix, and voids. Quantitative analyses were also performed.


All sections of the samples appear to have been produced with a clay paste that did not contain calcium carbonate but did include many angular, silt-sized inclusions of quartz and dark mica derived from igneous and metamorphic rocks ( Figure 1 ). The clay used to manufacture the ceramics may have been procured from deposits of wind-blown silt that is abundant in northwest China, including around Xi’an where the Terracotta Army is located. The clay paste of the terracotta warriors was prepared by the addition of sand (referred to as temper), which helps control shrinkage and improves resistance to thermal shock. Bricks lining the floor of a pit where warriors are located and rammed-earth samples from another pit were also analyzed. They seemed to have been fashioned from untempered clay. Sand temper could have been added to control the plasticity or “stickiness” of the fine clay and make it more suitable for shaping. The composition of the sand also indicated that it was collected in a loose form, rather than being produced by crushing sandstone. The possible source might have been alluvial sand found in the region. T e fi ring technology used on the statues has been debated extensively. Were they simply leſt to dry, fi red openly such as in a bonfi re, or fi red in an enclosed structure such as a kiln? T e presence of birefringence in the clay matrix of the samples suggests that they were not subjected to a sustained temperature above 850°C.


Why the Terracotta Army Foretold the Rise of the Chinese Empires


Stephen W. Carmichael Mayo Clinic , Rochester , MN 55905 carmichael.stephen@mayo.edu


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