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LAPIS NEPHRIT1CUS.
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LAPIS NEPHRITICUS: Jade.
This singular
mineral is a combination of magnesia and silica, with small proportions
of alumina and the oxides of iron and chrome. In colour it varies from
a soapy greenish white, with a waxy surface, to a clear agreeable
olive—the most esteemed shade. The Egyptian kind, Corsi states, is the
greenest of all, approximating in beauty to the Chrysoprase. This
substance is excessively hard, tough, and difficult to work, almost
insuperable by emery, and requiring the employment of diamond powder in
the operation. It therefore appears to have baffled the skill not
merely of the ancients, but even of the difficulty-courting artists of
the Eevival, no work exhibiting the well-known style of that period
existing in Jade ; and yet the latter had every inducement to essay
this material in the high reputation it enjoyed in their own times.
This
reputation rested upon its well-accredited virtue as a specific remedy,
or rather as a prophylactic, against all diseases of the kidneys, which
gives it its present popular name, corrupted by the French from pietra di hijada (kidney-stone)
as the Spaniards had christened it. They had introduced the stone
together with (as it would appear) the belief in its peculiar virtue
from the New World very soon after its discovery. In its efficacy even
the practical De Boot was evidently a firm believer ; and the prices
quoted by him equally testify to the general faith in its medicinal
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