Subrang1. K2O′ 7 ——— > —, potash extreme, perpotassic. Na2O′ 1
2. 7 5 “ < — > —, potash dominant, dopotassic. 1 3
3. 5 3 “ < — > —, potash and soda equal, sodipotassic. 3 5
4. 3 1 “ < — > —, soda dominant, dosodic. 5 7
5. 1 “ < —, soda extreme, persodic. 7

In classes IV and V rangs are formed by comparing femic MgO + FeO + CaO″ with femic alkalies K2O″ + Na2O″.

Minerals containing magnesia, iron, and lime are called mirlic.

Rang1. MgO + FeO + CaO″ 7 ———————— > —, extremely mirlic, permirlic. K2O″ + Na2O″ 1
2. 7 5 “ < — > —, dominantly mirlic, domirlic. 1 3
3. 5 3 “ < — > —, equally mirlic and alkalic, alkalimirlic. 3 5
4. 3 1 “ < — > —, dominantly alkalic, domalkalic. 5 7
5. 1 “ < —, extremely alkalic, peralkalic. 7

Sections of rangs distinguish between MgO + FeO and CaO″. Minerals with MgO + FeO are called miric.

Section1. MgO + FeO 7 ————— > —, extremely mirlic, permirlic. CaO″ 1
2. 7 5 “ < — > —, dominantly miric, domiric. 1 3
3. 5 3 “ < — > —, equally miric and calcic, calcimiric. 3 5
4. 3 1 “ < — > —, dominantly calcic, docalcic. 5 7
5. 1 “ < —, extremely calcic, percalcic. 7

Subrangs distinguish between MgO and FeO, thus:

Subrang1. MgO 7 —— > —, extremely magnesic, permagnesic. FeO 1
2. 7 5 “ < — > —, dominantly magnesic, domagnesic. 1 3
3. 5 3 “ < — > —, equally magnesic and ferrous, magnesiferrous. 3 5
4. 3 1 “ < — > —, dominantly ferrous, doferrous. 5 7
5. 1 “ < —, extremely ferrous, perferrous. 7

Finally a recognition of the character of the subordinate standard minerals leads to further subdivisions known as grads and subgrads. They only occur in classes II, III, and IV, because these are the only ones in which the subordinate minerals are in notable amounts. Grads are formed in a manner similar to that employed to produce orders. Thus grads in classes II and III correspond to orders in class IV and the reverse. Subgrads are the same in form as rangs when the difference in the treatment of salic and femic minerals is borne in mind. The names given to these divisions, which in fact recognize only the character of the magma, are derived from geographical localities and embrace many of those already in use, except that the names of orders are taken from countries or nations. Specific terminations indicate the place in the series of divisions:

ane for class, one for subclass.