Pargasite Root Name Group

The pargasite minerals are defined with 0.5 < ^A(Na+K+2Ca)<1.5 where Na or K is dominant and with the C position occupied by Mg or Fe²⁺ as dominant divalent ions and 0.5 < ^C(Al+Fe³⁺+Cr³⁺+V³⁺+2Ti) < 1.5 where Al is dominant, except for chromio-pargasite, which has Cr³⁺ as the dominant trivalent ion in the Z position (= IMA C position), and vanadio-pargasite, which has V³⁺ as the dominant trivalent ion in the Z position (= IMA C position). Note that if Fe³⁺ is instead the dominant Z trivalent cation (= IMA C position), the root name is not "ferri-pargasite", but instead becomes hastingsite.
The W position may contain (OH), F or Cl.

The individual pargasite minerals are defined by their dominant element in the A, Z²⁺ (= IMA C²⁺) and W position.

In mindat.org we avoid using variables with the same symbol as elements and deviate from the IMA nomenclaure in that we use X rather than B, Z rather than C and (OH,F,Cl,O) rather than W.

Calcium Amphibole Subgroup > w(OH, F, Cl)-dominant Amphibole Group > Amphibole Supergroup