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Webster 1913 Edition

Adj.

[L.

argilla

white clay +

-ferous

Producing clay; – applied to such earths as abound with argil.

Kirwan.

Adj.

[L. argilla, clay, and fero, to produce.] Producing clay; applied to such earths as abound with argil.

argilliferous ‎(comparative more argilliferous, superlative most argilliferous)

(geology) Producing clay; rich in argil.

argilliferous earths

(Can we find and add a quotation of Kirwan to this entry?)

rich in clay