nouna white, colourless, pink, or green mineral consisting of a hydrated silicate of calcium, potassium, and fluorine in tetragonal crystalline form. It occurs in cracks in volcanic rocks. Formula: KCa4(Si4O10)2(OH1F).8H2O
Word origin
C19: from French, from
apo- + Greek
phullon leaf +
-ite1; referring to its tendency to exfoliate