Some mineralogists, following Sir D.
Stone coal is also a local English term, but with a signification restricted to the substance known by mineralogists as anthracite.
By modern mineralogists the name chalcedony is restricted to those kinds of silica which occur not in distinct crystals like ordinary quartz, but in concretionary, mammillated or stalactitic forms, which break with a fine splintery fracture, and display a delicate fibrous structure.
Optical examination of many chalcedonic minerals by French mineralogists has shown that they are aggregates of various fibrous crystalline bodies differing from each other in certain optical characters, whence they are distinguished as separate minerals under such names as calcedonite,pseudocalcedonite,quartzine, lutecite and lussatite.
To mineralogists rock-salt is often known as halite - a name suggested in 1847 by E.