Londonite

specimen number:
2354288

location:
Antsongombato Mine, Anosiarivo Manapa, Vakinankaratra, Madagascar

description:
A sharp slightly translucent lustrous yellowish green crystal of londonite without matrix. In good condition.

The Antsongombato Mine in the Vakinankaratra region of Madagascar is situated within complex Precambrian metamorphic terrain that hosts highly fractionated, lithium-rich granitic pegmatite dikes. These narrow, steeply dipping pegmatites formed during late-stage magmatic crystallization, creating localized chemical environments enriched in rare elements like cesium, beryllium, and boron. Historically worked by hand since the early twentieth century and extensively targeted by small-scale artisanal miners and mineral collectors for exceptional tourmaline and rare-element species, the deposit is especially famous for producing world-class specimens of londonite. Londonite is an extremely rare cesium-dominant borate mineral that forms durable isometric crystals ranging from colorless to sulfur-yellow, closely mimicking its potassium analogue rhodizite within the core zones of these evolved Malagasy pegmatites.

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