Editing Amphibole (section)

===Series===
Certain amphibole minerals form solid solution series, at least at elevated temperature. Ferrous iron usually substitutes freely for magnesium in amphiboles to form continuous solid solution series between magnesium-rich and iron-rich endmembers. These include the cummington (magnesium) to grunerite (iron) endmembers, where the dividing line is placed at 30% magnesium.{{sfn|Nesse|2000|pp=277-290}}

In addition, the orthoamphiboles, anthophyllite and gedrite, which differ in their aluminium content, form a continuous solid solution at elevated temperature. As the amphibole cools, the two end members exsolve to form very thin layers (lamellae).{{sfn|Nesse|2000|pp=277-290}}

Hornblende is highly variable in composition, and includes at least five solid solution series: magnesiohornblende-ferrohornblende ({{chem2|Ca2[(Mg,Fe)4Al]Si7AlO22(OH)2}}), tschermakite-ferrotschermakite ({{chem2|Ca2[(Mg,Fe)3Al2]Si6Al2O22(OH)2}}), edenite-ferroedenite ({{chem2|NaCa2(Mg,Fe)5Si7AlO22(OH)2}}), pargasite-ferropargasite ({{chem2|NaCa2[(Mg,Fe)4Al]Si6Al2O22(OH)2}}) and magnesiohastingstite-hastingsite ({{chem2|NaCa2[(Mg,Fe)4Fe^{3+}]Si6Al2O22(OH)2}}). In addition, titanium, manganese, or chromium can substitute for some of the cations and oxygen, fluorine, or chlorine for some of the hydroxide. The different chemical types are almost impossible to distinguish even by optical or X-ray methods, and detailed chemical analysis using an electron microprobe is required.{{sfn|Nesse|2000|p=285}}

Glaucophane to riebeckite form yet another solid solution series, which also extends towards hornblende and arfvedsonite.{{sfn|Nesse|2000|p=287}}

There is ''not'' a continuous series between calcic clinoamphiboles, such as hornblende, and low-calcium amphiboles, such as orthoamphiboles or the cummingtonite-grunerite series. Compositions intermediate in calcium are almost nonexistent in nature.{{sfn|Nesse|2000|p=279}} However, there is a solid solution series between hornblende and tremolite-actinolite at elevated temperature. A [[miscibility gap]] exists at lower temperatures, and, as a result, hornblende often contains exsolution lamellae of grunerite.{{sfn|Klein|Hurlbut|1993|p=496}}