Geological Survey of India The Monolith of Lord Buddha: A Type Sample of Granite (s.s.) A field party of Project: Precambrian Geology, Operation: Andhra Pradesh, Southern Region in 1996, had collected in situ rock samples from the exact location in the field where a monolith of Lord Buddha was sculpted. The monolith which is 57 ft tall, 10 ft broad and 9 ft thick, and weighing about 400 tonnes is now located at the centre of the Husain Sagar Tank, (Figure-1) Hyderabad, Andhra Pradesh. This monolith was carved out of a dome-shaped mound by name Venkateshwara Gutta situated at about 55 km east-northeast of Hyderabad on the Hyderabad-Warangal State Highway. The field party comprising Dr. H. Sarvothaman, Dr. K. N. Srinivasan and Shri G. Suresh, then Geologists (Sr) had studied the rock samples for petrography and petrochemistry. These samples are coarse, equigranular and uniform grained throughout the monolith. Point-count on minerals in thin sections of these samples and modal analysis indicated 33.5% quartz, 36% perthitic-microcline, 25.5% plagioclase and 2.3% biotite. The samples contain accessory minerals such as myrmekite (1%), opaque minerals (0.7%), sphene (0.4%), epidote (0.3%) and apatite (0.3%) constituting 2.7%. The modal plot in the quartz-alkali feldspar-plagioclase (QAP) diagram (Figure-2) indicates the composition of granite (s.s.). The modal mineral composition is shown in Figure-3. Chemical analysis of one sample reveals that it contains 74.08% SiO2, 13.42% Al2O3, 1.05% total iron expressed as Fe2O3, 0.54% MgO, 1.4% CaO, 3.35% Na2O, 5.24% K2O, 0.19% TiO2 and 0,05% sulphur. The CIPW Normative composition of the granite sample is as follows: Quartz-30.06%, orthoclase-31.14%, albite-28.3%, anorthite-6.12%, diopside-3.47% and ilmenite-0.3%. The plot of this sample in the normative Ab-An-Or diagram lies in the field of ‘granite’ (Figure-4). Its molar Al2O3 / (CaO + Na2O + K2O) ratio is 0.98, which indicates subaluminous or metaluminous nature. Contributed by Southern Region Geological Survey of India Based on the mineralogical and chemical studies, it is concluded that the rock from which the monolith of Lord Buddha was sculpted is a subaluminous to metaluminous granite (s.s.). Therefore, the monolith of Lord Buddha may be regarded as a type sample of Granite (sensu stricto). Figure-1 Contributed by Southern Region Geological Survey of India Figure-2 Contributed by Southern Region Geological Survey of India Figure-3 Quartz Perthitic-microcline Plagioclase Biotite Accessory minerals Figure-4 Contributed by Southern Region