Chemistry Reference
In-Depth Information
CaFe
3+
AISiO
6
Esseneite
Kushiroite
Diopside
CaAIAISiO
6
Ca(Mg,Fe
2+
,Mn)Si
2
O
6
Figure 3.23
Fassaites: exemple of pyroxenes from skarns in Roumanie (after M-L Pascal,
2005, modified).
Jadeite
is the NaAlSi
2
O
6
end member; intermediate terms with diop-
side are called
omphacite
. Omphacites rich in ferric iron (intermediate
between omphacite and aegirine) are called chloromelanites. These are
minerals of high pressure metamorphism.
2 The iron-bearing sodic pyroxenes derived from diopside by
substitution:
Ca Mg
Na Fe
3+
The NaFeSi
2
O
6
end member is
aegirine
(or acmite). The intermediate
terms are called
aegirine augite
. Notice the fact that there is no solid
solution between augite and aegirine and that the solid solution occurs
between members of the diopside - hedenbergite series and aegirine.
These are minerals of differentiated alkaline igneous rocks: volcanic
(phonolites) and plutonic (nepheline syenites).
Spodumene
Lithium pyroxene
is
spodumene
LiAlSi
2
O
6
. This mineral occurs in lithium gra-
nitic pegmatites with quartz, albite, lepidolite, beryl and petalite (LiAlSi
4
O
10
).
