Calcedon

Merchandise invoiced as calcedon, classified at 60 per cent ad valorem under paragraph 1528, tariff act of 1930, is claimed to consist of imitation semiprecious stones, faceted, dutiable at 20 per cent under the same paragraph.

A yellowish-red carnelian is a calcedon. Is found–among other places–in India. […] Like carnelian, agate is a calcedon.

It consisted of small, rounded rock-boulders with calcedon and pieces of jasper.

No part besides must of they selfe be known. But by the topaz, Opal, Calcedon.

In this, the final chapter of the "Calc." saga, it can be stated that the that the abbreviation in question really does stand for calcedon, a theorbo-type instrument.

Indeed, the calcedon seems principally intended as a reinforcement to the cello: where the cello and keyboard parts differ from one another, the calcedon goes with the bowed instrument.

At another private concert at Count Caldarinii's house in Bologna (1715), Caldarinii played alternately the lute and the calcedon.

Christus is um unsrer Missetat willen, TVWV 1:151, 1721, scored for soprano, alto, tenor, and bass, two violins, viola, cello, organ, two oboes, two D clarinets, calcedon (bass lute), and organ.