Geochemistry of sauceboats excavated from Independence National Historical Park (Philadelphia): evidence for a Bonnin and Morris (c. 1770e73) provenance and implications for the development of nascent American porcelain wares

摘要

Porcelain sauceboats excavated from a privy with a late 18th century (1786 or later) context at IndependenceNational Historical Park (INHP) are anomalously Al-rich compared with previously analysed Anglo-American sulphurous phosphatic wares. Apart from their S content, they are most similar to phosphatic Wm Reid porcelain (Brownlow Hill, Liverpool, c. 1755e67, and its branch at Shelton, Staffordshire) in terms of their major element constituents, but they contain heavy minerals (e.g., TiO_2 polymorphs) and in this regard resemble a dated (1773) silicious-aluminous-calcic (S-A-C) Bonnin and Morris porcelain (Philadelphia) openwork porcelain basket. In terms of morphology and composition, some TiO_2 polymorphs in the 1773 basket match those from clay from White Clay Creek, Delaware, a resource reputedly exploited by Bonnin and Morris. Their high Nb/Cr ratios indicate derivation from a metapelitic (or granitic pegmatite) source. So too do some from the INHP sauceboats, although others are chrome-rich (w1% Cr_2O_3), indicating a mafic source. The bedrock beneath White Clay Creek includes metasediments, granitic pegmatite, and metabasites (e.g., of the Wissahickon Formation), pointing to a local source for the TiO_2 polymorphs in the porcelains described here. Although the evidence for a Bonnin and Morris provenance for the INHP sauceboats is circumstantial, their enrichment in heavy minerals, unusual e perhaps experimental e compositions, and aesthetic characteristics nonetheless suggest a Philadelphia origin for these artifacts. The compositions of 18th century Philadelphia porcelain support the contention that knowledge of phosphatic and S-A-C pastes originating in London was transferred first to Staffordshire and Liverpool, and then to Philadelphia, perhaps via a potter by the name of Wm Ball.