Asbestos-Based Pottery from Corsica: The First Fiber-Reinforced Ceramic Matrix Composite

Our plain-English summary of Asbestos-Based Pottery from Corsica: The First Fiber-Reinforced Ceramic Matrix Composite, by P. Colomban, A. Kremenović (Materials, 2020).

The study

• Authors: P. Colomban, A. Kremenović
• Journal: Materials
• Published: 2020;13(16)
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos-containing pottery shards collected in the northeast of Corsica (Cap Corse) and dating from the 19th century, or earlier, have been analyzed by SEM-EDS, XRPD, FTIR and Raman microspectroscopy. Blue (crocidolite) and white (chrysotile) asbestos fiber bundles are observed in cross-sections. Most of the asbestos is partly or totally dehydroxylated, and some transformation to forsterite is observed to occur, indicative of a firing above 800 °C. Examination of freshly fractured pieces shows a nonbrittle fracture with fiber pull-out, consistent with a composite material behavior, which makes these ceramics the oldest fiber-reinforced ceramic matrix composite. Residues indicate the use of this pottery as a crucible for gold extraction using cyanide.

In plain English

This was a laboratory analysis of four asbestos-containing pottery shards from the northeast of Corsica. The shards were supplied by the Corsican Archaeological Office and chosen because their colors differed. Their exact origin was not known. The authors examined them with microscopes, electron microscopy with elemental analysis, X-ray diffraction, and infrared and Raman spectroscopy. Individual fibers measured about 100 nm to 1 µm across and up to a few centimeters long. The minerals varied by shard and included antigorite, actinolite, tremolite and crocidolite. The authors reported finding blue (crocidolite) and white (chrysotile) asbestos. Firing had altered much of the material, but the fibers were generally preserved and pulled out over several millimeters where the pieces broke. A spectral signal matching a gold cyanide compound led the authors to conclude that one shard had been used as a crucible for gold extraction. The authors also concluded that the potters selected the most appropriate asbestos fibers. They noted that the X-ray diffraction amounts were not fully reliable. The study did not examine human exposure or health.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory materials analysis (archaeometry) of archaeological pottery shards using optical and electron microscopy with elemental analysis (SEM-EDS), X-ray powder diffraction (XRPD), infrared (FTIR) and Raman spectroscopy
• Who was studied: Four pottery shards supplied by the Corsican Archaeological Office (DRAC). They were selected for their differing colors from samples collected by Corsican scholars in northeast Corsica during the 19th and 20th centuries. Their exact provenances were not known.
• Exposure: Asbestos and related minerals mixed into fired, unglazed pottery. Crocidolite was found by X-ray diffraction in samples b and d, and tremolite in samples b and c. Antigorite, actinolite and chlorite–serpentine were also identified.
• Main results:
  • Individual fibers in the shards measured about 100 nm to 1 µm in diameter and could reach a few centimeters in length.
  • Sample c contained a larger amount of tremolite, with minor diopside, actinolite, talc and quartz.
  • Sample d contained large amounts of antigorite and chlorite–serpentine, with minor heated actinolite, crocidolite (riebeckite), talc and quartz.
  • The authors identified blue and white asbestos in the pottery and interpreted this as the potters selecting the best quality fibers available.
  • Signals of the original hydroxyl groups survived only in the cores of grains, which the authors attributed to dehydroxylation during firing.
  • Despite firing, the fibers were generally preserved, shown by fiber pull-out over several millimeters at fractures.
  • In sample d, fiber bundles could not be seen by optical or scanning electron microscopy. The authors attributed this most likely to a higher degree of reaction between phases.
  • A Raman peak at 2165 cm−1 matched the gold cyanide compound KAu(CN)2. The authors noted that the conservation glue cyanoacrylate shows a band at about 2250 cm−1 instead.
  • The authors concluded that traces of KAu(CN)2 showed that one shard had been used as a crucible for gold extraction or separation.
• The authors' conclusion: The authors concluded that ancient potters selected the most appropriate asbestos fibers for these fiber-reinforced ceramics.
• Limitations the authors state:
  • Quantitative X-ray diffraction analysis was not completely reliable because the fibers were preferentially oriented.
  • The exact provenances of the shards were not known.
  • Identifying specific minerals was difficult, especially where firing had degraded their structures.
  • Actinolite, tremolite and crocidolite were hard to tell apart in the complex X-ray diffraction patterns.
  • The error of the elemental analysis was estimated below 10%, except for aluminum.

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Chrysotile, Forsterite.

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