Preliminary Geochemistry of Topaz Occurrence in A-Type Granites around Massange Area, Central Nigeria

The Massange Topaz is a gem mineral with chemical composition of Al 2 SiO 4 (F,OH) 2 and is found as alluvial deposits within the Sha-Kaleri A-type Granite Complex (SAGC) in central Nigeria. A total of sixteen (16) samples were collected and analyzed for major oxides (SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, P 2 O 5 , K 2 O, Na 2 O, TiO 2 and MgO), major elements (F, Cu and Zn) and trace elements (Rb, Zr, Br, Cr, Ba and Sr) to determine variety in elemental constitution of the gems and rocks. Massange topaz is rich in fluorine and alumina. The fluorine in its composition is a determinant factor on its formation because it is a necessary ingredient in hydrothermal fluid for the formation of topaz. This paper will focus on why the topaz deposits in the study area are concealed in the subsurface and why the mineralizing fluid crystallized to topaz leaving out other gem types. Also, the authors will attempt to describe the rock units that host the mineralization of the topaz and the elements that led to the resultant gem properties. This research work also considers the enhancement of gemstones for better value in a bid to make them more appreciable in Nigeria.