The Vanadium-bearing Oxide Minerals of the Green Giant Vanadium-graphite Deposit, Southwest MadagascarThe Vanadium-bearing Oxides of the Green Giant Deposit, Madagascar

Rare vanadium-rich oxide minerals have been previously identified in graphite-bearing quartzo-feldspathic gneisses derived from shale protoliths. In this work, such minerals are described from the Green Giant vanadium-graphite property in southwest Madagascar. The vanadium-rich oxides include vanadium-bearing rutile (2.88 ± 1.75% V2O3, n = 18), schreyerite, oxyvanite, and karelianite. These minerals have been previously identified together in the Sludyanka, Lake Baikal area. Green Giant is the second occurrence worldwide of oxyvanite, and within the oxyvanite–berdesinskiite solid solution series Green Giant oxyvanites are the closest to endmember, with an average calculated mineral formula of (V3+1.49,Cr0.50,Fe3+0.01)∑2.00V4+1.00O5. Also found in this study is an unknown vanadium-titanium oxide mineral, UK1, which has a calculated formula of (V3+1.67Cr3+0.26 Al0.06)∑1.99(V4+2.05Ti4+1.94)∑3.99O11 and may be related to the V2Ti4O11 reported previously from the Lake Baikal area.