Rounded olivine crysts in these kimberlites show various stages of recrystallization and serpentinised alteration. They are clearly derived from mantle depth, but dependent on the phases of emplacement, the olivine may be completely replaced by pseudomorphs, or entirely absent leaving pitted rims. These examples are from fresh cut samples that have been protected from weathering and exposure until they were mine excavated at depth. Included is an example of fresh olivine xenoliths from Lanzarote displaying more angular crystals.

#olivine #mantle #structure

A look at phlogopite occurrence associated with the kimberlite in this part of the world, Limpopo Province, South Africa. Fresh macrocrystic and groundmass phlogopite is encountered at depth, while its type 2 evolved product, tetraferriphlogopite is found some distance on trend with the kimberlite dyke systems. These phlogopite examples are hosted in a variety of exposures and samples gathered from the field and historic mine workings over the course of 2019-2022, and represent the array of groundmass and macrocrystic phlogopite displaying a variety of pale to dark colours; excavated from depth (fresh brown samples), and its alteration products found in rare exposure; darker iron-rich groundmass tetraferriphlogopite representing different evolutions. The phlogopite has not been seen in more common aphantic kimberlite outcrop, the latter tends to be fine grained and undergone significant serpentinisation
#phlogopite #kimberlite #magmatism #mantle #structure