Note: Argentine is a pearly lamellar variety; aphrite is
foliated or chalklike; dogtooth spar, a form in acute
rhombohedral or scalenohedral crystals; calc-sinter and
calc-tufa are lose or porous varieties formed in
caverns or wet grounds from calcareous deposits; agaric
mineral is a soft, white friable variety of similar
origin; stalaclite and stalagmite are varieties formed
from the drillings in caverns. Iceland spar is a
transparent variety, exhibiting the strong double
refraction of the species, and hence is called doubly
refracting spar.