Lac Alaotra Chrysoberyl Pegmatites
Ambatondrazaka District, Alaotra-Mangoro, Madagascar
Pegmatita misy krysoberila, Distrikan' Ambatondrazaka, Faritr' Alaotra-Mangoro, Faritanin'i Toamasina, Madagasikara
Key Information
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The Lac Alaotra Chrysoberyl Pegmatites are located near Lake Alaotra in Ambatondrazaka District, Alaotra-Mangoro, Madagascar, known for its rice fields and scenic beauty.
Research suggests chrysoberyl, beryl, and other minerals like biotite and dumortierite are found here, with chrysoberyl being the highlight for its gem-quality crystals.
It seems likely that the geological structure involves granite pegmatites formed from cooling magma, hosting these minerals.
The evidence leans toward small-scale, artisanal mining, possibly active for decades, though specific historical details are limited.
The local culture is agricultural, centered on rice, with traditional music and dance, and the climate is tropical with wet and dry seasons affecting farming.
Geographic Location
The Lac Alaotra Chrysoberyl Pegmatites lie on the eastern side of Lake Alaotra, the largest freshwater lake in Madagascar, within the Ambatondrazaka District of the Alaotra-Mangoro region. This area, about 101 km northeast of the capital Antananarivo, is surrounded by rolling hills and vast rice fields, earning it the nickname "rice granary of Madagascar." The nearby town of Ambatondrazaka, the regional capital, is accessible via Route Nationale 44 and offers a glimpse into local life with its markets and historical significance.
Minerals Produced
Chrysoberyl is the star attraction, known for its yellow-green, gem-quality crystals, often found in twinned forms. Other minerals include beryl, biotite, dumortierite, microcline, and quartz, adding to the locality's mineralogical richness. These pegmatite-hosted gems are prized by collectors for their rarity and beauty.
Geological Structure
The pegmatites here are granite-based, formed from the slow cooling of magma deep within the Earth. This process created coarse-grained rocks rich in minerals like chrysoberyl, which formed under specific chemical conditions during crystallization. The surrounding rock provides a natural showcase for these geological treasures.
Mining History
Mining appears to be small-scale and artisanal, likely ongoing for decades, given references to collections and auctions. While specific start dates and ownership details are scarce, the locality is known among mineral enthusiasts for its chrysoberyl, suggesting a long history of exploration and collection.
Local Culture and Characteristics
Ambatondrazaka's culture is deeply tied to agriculture, with rice as the staple crop. The community celebrates with traditional music, dance, and cuisine, reflecting a blend of Malagasy heritage and influences from Southeast Asia and East Africa. The area's history, dating back to the late 18th century with figures like Randriambololona, adds a layer of cultural depth.
Climate and Ecology
The region has a tropical climate with a wet season (November to April) and a dry season (May to October), with temperatures ranging from 53°F to 83°F. This climate supports rice farming but may influence the exposure of mineral deposits through erosion. The ecology around Lake Alaotra is diverse, with wetlands hosting endemic species, crucial for both biodiversity and local livelihoods.