First explicit statement of the principles of pearl valuation

Jeffries, David. A treatise on diamonds and pearls. In which their importance is considered; and plain rules are exhibited for ascertaining the value of both. The fourth edition, with large improvements.

London, E. Lumley, [1871].

8vo. XVI, 116 pp. With 30 plates. Contemporary blue cloth, covers blindstamped and upper cover gilt, title gilt to spine.

 1.800,00

A 19th century edition of the "first book in English to describe how diamonds and pearls can be evaluated on the basis of the factors of size (or weight) and style of cut" (Sinkankas). The London jeweller Jeffries is also the first author to provide "a clear statement of the principle that the value of pearls should be calculated to the square of their weight [...] This principle is implicit in the valuation tables given by earlier authors, including Tavernier and others, but Jeffries is the first to state it explicitly. At the back of his book, he provides tables allowing the calculation of the value of individual and batches of pearls of different size or quality. This is effectively a 'chau' book, as used by merchants in the Gulf and India until the mid-20th century, and fulfils exactly the same function" (Carter).

"The text explains the [diamond] cutting procedure, how the evaluation rules were derived, the importance of imperfections and flaws as affecting price, notes on rough diamonds [...] and finally, a somewhat similar procedure for the valuation of pearls, with highest values accorded to pearls of closest approach to spherical perfection, luster, etc. The mathematical rule used for the pearl is known as the 'square of the weight' multiplied by a per-carat base price" (Sinkankas).

Insignificant browning. Removed from the Library of the Birmingham Assay Office, one of the four assay offices in the United Kingdom, with their library stamp to the flyleaf.

OCLC 31561438. Cf. Sinkankas 3195. Carter, Sea of Pearls, p. 83, 125f., 251. Goldsmiths' 8500. Hoover 453 (note). Roller/G. II, 10.