calcedon

noun2

1. •
   The bass lute, an instrument used by baroque composers (notably Telemann).

   • 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. — 1985
2. •
   (old-fashioned) Any common mineral, such as chalcedony or calcite, that is found as an intrusion or vein in another stone, especially in a precious stone.

   • A yellowish-red carnelian is a calcedon. Is found–among other places–in India. […] Like carnelian, agate is a calcedon. — 1941