Terra sigillata
Lemnian earth, “sealed earth”
- Known today as
- A clay dug on the island of Lemnos and stamped with a seal.
- Kind
- Mineral, in 1 older authority
- Constituents
- kaolinite and smectite clays, iron oxides, alum
- Earliest authority here
- Galen (AD 129–c. 216)
- In other databases
- Wikidata search
Terra sigillata: what was it used for?
The antidote clay: against poisons, bites, and the plague.
Terra sigillata: what does modern science say?
Some clays bind toxins in the gut, which may explain part of its fame.
Pharmacognosy & Toxicology
- Constituents
- kaolinite and smectite clays
- iron oxides
- alumin some sealed earths
- Mechanism
- A clay like Armenian bole: it adsorbs, dries, and firms the stool, and its smectite component binds some toxins and bacteria in the gut, as diosmectite does today. Analysis of surviving Lemnian earth tablets (Photos-Jones, 2008) found an ordinary illite-kaolinite clay. The seal guaranteed the source, which was the first trademark of a drug.
- Toxic dose
- Safe; some clays carry lead and arsenic.
- Standing
- Obsolete as a brand; the clay class survives as kaolin and diosmectite.
- Photos-Jones, E., and Hall, A. J. (2011). Lemnian Earth and the Earths of the Aegean: An Archaeological Guide to Medicines, Pigments and Washing Powders. Potingair Press. Book, seen in reviews
- Dupont, C., and Vernisse, B. (2009). “Anti-diarrheal effects of diosmectite.” Paediatric Drugs 11. Verified against its record · doi:10.2165/00148581-200911020-00001
The abstract of each source, beneath its citation. For Club members. About the Club or sign in.
Constituent names open the compound’s record at PubChem, and “ChEMBL” beside a name opens its record at ChEMBL, the European Bioinformatics Institute’s database of bioactive molecules. Where a mechanism line was checked against ChEMBL (ChEMBL 37, read 1 October 2026), the check is shown with the measured value and its source paper, or says plainly that nothing has been measured. Doses are as the references give them, for description only; this is not medical advice. Each source carries the result of its check against Crossref, PubMed, or the authority’s page: see Verification.
What Medicine Makes of It
- The PlagueThe pomander and the vinegar, the flea and the bacillus.
- The Universal AntidoteBezoar, unicorn, and theriac against every poison, and what replaced them.
Terra sigillata: what lore surrounds it?
The seal was a guarantee against counterfeits, which were everywhere; in later centuries it was the Ottoman sultan’s.
Terra sigillata: what did the older authorities say?
- Galen
- Sailed to Lemnos to see the earth dug and sealed by the priestess, and brought twenty thousand of the stamped tablets home.
Sources
- Galen, On the Powers of Simple Medicines IX. Primary text
Verification
- Checked
- October 1, 2026
- Passes
- Every sentence read against its sources, in the pass over the remaining 343 entries
- The Standing line checked against the authority it names (EMA, WHO, FDA, CITES, Commission E)
- Every dated or regulatory claim checked by category across the database
- Sources
- 3 cited: 1 verified against its record, 1 primary text, 1 book, seen in reviews. 1 with the abstract on file.
- Corrections
- None were needed.
What was checked, how, and what was found is set out on the Verification page. A checked source is one whose record was found; it does not make the entry medical advice.
Cite This Entry
Version 1 · first published September 25, 2026
- Chicago
“Terra sigillata.” In Materia Medica, edited by B. C. P. Statema. Version 1. The Thinking Press, 2026–. Last modified September 25, 2026. https://thethinkingpress.org/materia-medica/terra-sigillata.
- MLA
“Terra sigillata.” Materia Medica, edited by B. C. P. Statema, version 1, The Thinking Press, 25 Sept. 2026, thethinkingpress.org/materia-medica/terra-sigillata. Accessed 8 Oct. 2026.
- APA
Terra sigillata. (2026, September 25). In B. C. P. Statema (Ed.), Materia medica (Version 1). The Thinking Press. Retrieved October 8, 2026, from https://thethinkingpress.org/materia-medica/terra-sigillata
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See Also
Sharing iron oxides
Also in Galen
Theriac in Galen · Purslane in Galen · Peony in Galen · everything Galen names →
Drawing on the same sources: Galen, Photos-Jones, Dupont
Nearby in the alphabet
Tetragrammaton (not pronounced in Jewish practice) · Teonanácatl (Small brown mushrooms that stain blue when bruised) · Teasel (Dipsacus fullonum) · Thorn apple (of the nightshade family) · Tea (The dried leaves of Camellia sinensis) · The thurible · Tansy (Tanacetum vulgare)
Historical description, not medical advice.