Quartz after Melanophlogite

specimen number:
2072302

location:
Farm Ysterputs 254, Blinkpan, Namibia

description:
The top of this attractive blue banded quartz matrix is covered with blocky crystals of what were once melanophlogite measuring to 0.4 cm in size, these now replaced by light blue colored quartz. In good condition. The base of this piece has been cut and polished to show the attractive banding within the matrix.

Farm Ysterputs 254, located near Blinkpan in the Karas Region of southern Namibia, is a globally recognized mineralogical site situated within the extensive Karoo basalt flows. Geologically, the deposit is characterized by hydrothermal activity that occurred within the vesicles and fractures of the volcanic host rock, where silica-rich fluids precipitated various forms of quartz. The locality is specifically famous for producing exceptional specimens of quartz after melanophlogite, where the quartz has completely replaced the rare cubic silica polymorph while retaining its original crystal habit. Historically, the farm has seen intermittent small-scale mining and quarrying activities primarily focused on specimen recovery rather than industrial ore production. Systematic collecting and exploration for these unique silica structures gained significant momentum in the late 20th century and has continued sporadically through 2026. Today, Farm Ysterputs remains the premier locality for these sharp, lustrous pseudomorphs, which are prized by researchers and collectors for their geometric precision and the insight they provide into the complex mineralogical history of the Namibian volcanic fields.

The phenomenon observed at this site is known as a pseudomorph, a term derived from Greek roots meaning "false form." In mineralogy, a pseudomorph occurs when one mineral replaces another in such a way that the internal chemistry and structure change, but the outward appearance and crystal shape of the original mineral are preserved. At Farm Ysterputs, the original melanophlogite crystals formed as distinct cubes or multifaceted blocks, but because melanophlogite is chemically unstable under certain conditions, it was later dissolved or transformed. As silica-rich groundwater moved through the rock, it deposited quartz into the space previously occupied by the melanophlogite. This process results in a specimen that looks like a cube (the habit of melanophlogite) but is actually composed entirely of quartz, providing a permanent "mineral fossil" of a species that no longer exists in that specific sample.

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