New Localities In Madagascar

Federico Pezzotta is an expert on Madagascar, and pezzottaite is named after him. The author also provides the geological landscape + the unique particularities of the gem deposits in Madagascar. Many experts believe Madagascar is vast with poor infrastructure + a virgin territory + there may be more surprises from from this island. Keep in touch.

Federico Pezzotta (Natural History Museum, Milan, Italy) writes:

Madagascar is host to an abundance and variety of gem materials as a result of its long and complex geologic history. The upper Archean to Neoproterozoic crystalline basement of Madagascar experienced locally unusual and even unique geologic conditions during several mountain-building events. Erosion of these rocks occurred during the late to post-tectonic uplift of the basement, and deposited Permian-Mesozoic sediments along the western margin of the Mozambique basin, locally forming immense paleoplacer deposits (e.g Ilakaka). More recently, the morphologic and climatic conditions of the island during the past few million years resulted in the formation of abundant secondary residual and alluvial gem deposits.

Even though research and mining of Madagascar’s gems has continued for more than a century, many large areas in the island remain poorly explored and have significant potential for the discovery of new deposits. Within the last few years, the country’s improved political situation has allowed for important developments in the scientific research, mining, and trading of gems.
Recently, two major discoveries occurred in Madagascar, both in Fianarantosa Province: (1) a series of multicolored tourmaline deposits, of both primary and residual nature, in a large area between the villages of Ambatofitorahana and Ambohimasoa, along the national road connecting the towns of Ambositra and Fianarantosoa; and (2) a multicolored sapphire deposit of residual nature located 17km south of the village of Ranotsara, southeast of the town of Ihosy.

The tourmaline deposits are related to a large rare-element miarolitic pegmatite field, surprisingly rather undocumented in the available geologic maps, that extends in a northeast-southwest direction for a distance of ~40km. Initial discoveries of tourmaline in the area were made in 1995-1996 with the mining of the primary and secondary residual deposits of Valozoro, a few kilometers southeast of Ambatofitorahana. No additional significant discoveries were made until August-September 2005 when, in the Anjoma area (located a few kilometers southwest of Ambatofitorahana), an enormous quantity of multicolored tourmaline (weighing several tones, but mainly of carving quality) was found close to the surface at Anjomanandihizna (also known as Nandihizana). Soon afterward, additional multicolored tourmaline deposits were discovered south of this area; the most important ones at Fiadanana (a few kilometers south of Valozoro), Ankitsikitsika (about 15 km south of Anjomanandihizana), and Antsengy (northwest of the village of Ambohimahasoa). Local gem dealers refer to this entire area as Camp Robin, from the name of a village in center of the district in which much of the gem trading occurs.

The new sapphire deposit, named Marosely, was discovered in October 2005. Transparent bipyramidal sapphire crystals, with colors ranging from blue to purple and, rarely, purplish red (ruby), have been recovered mainly in small size (less than 0.4 g). Larger crystals of gem quality are rare, but occasionally they exceed 2 g and produce good size cut stones. These crystals originated from the high grade metamorphic bedrock, and were concentrated in near-surface residual deposits through erosion. The total production of sapphire rough from Marosely, through June 2006 is estimated at about 500 kg.