ELLENDALE LAMPROITE LAVA
Western Australia's Ellendale Lamproite Field contains diamondiferous lamproite intrusions. What's more interesting, really, from a volcanics point-of-view, is that lamproite lava (= extrusive lamproite) is associated with some of the Ellendale lamproite bodies. Lamproite lava is a rare rock type (ordinary intrusive lamproite pipes themselves are not super-common either). The rock shown below is a lamproite lava sample that's gorgeous in a way that the photos can't convey.
The unweathered matrix is light gray-brown, and the large phenocrysts (black-looking or dark brown-looking or sparkly white in the photos below) are wonderfully lustrous golden-brown phlogopite mica crystals (ideally KMg3(Si3Al)O10(F,OH)2 - potassium-magnesium hydroxy-fluoro-aluminosilicate). Many of them display well-defined hexagonal crystal structures. I'm not exactly sure about the mineral content of the matrix - it possibly has titanate minerals (having TiO3) or armalcolite ((Mg,Fe,Al)(Ti,Fe)2O5).
This rock comes from the Ellendale Center No. 5, a subcommercially diamondiferous lamproite body in the Ellendale Lamproite Field (northeastern margin of the Canning Basin, Kimberley, northern Western Australia). This Ellendale lamproite lava is Early Miocene in age (19-22 m.y.).
Phlogopite leucite lamproite lava (field of view ~7.5 cm across) from the Ellendale Center No. 5 (Lower Miocene, 19-22 m.y.), Western Australia.
Phlogopite leucite lamproite lava (field of view ~3.5 cm across) from the Ellendale Center No. 5 (Lower Miocene, 19-22 m.y.), Western Australia.
Most info. provided by Tony Peterson.