Thus calcspar is in the 2nd, or hexagonal, whilst aragonite is in the 4th, the rhombic, system, yet both are the same substance, viz.
"The Chemistry, Properties and Tests of Precious Stones"
John Mastin
105; and on the rings of aragonite deposited from solution, see Gustav Rose in vol.
"COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1"
Alexander von Humboldt