Abstract:
Pulmoddai and Verugal are two economically important heavy mineral beach placer deposits located on
the northeast coast of Sri Lanka. Pulmoddai deposit is situated northward from the Mahaweli River mouth
while the Verugal deposit is situated southward from the river mouth. At present, Pulmoddai is exploited
for Ti and Zr raw material, whereas Verugal deposit is still in exploration stage. In the present study, we
investigate and compare heavy mineral composition of selected locations along Mahaweli River and
Pulmoddai and Verugal deposits to understand the river contribution of sediments towards these placer
deposits. Sediment samples were collected from representative places along the Mahaweli River and both
placer deposits. Sieve analysis was carried out to identify the textural significance. Panning was done to
separate heavy minerals from the samples. Accuracy and reliability of panning process was tested using
bromoform test. Grain counting method through a petrological microscope was used to analyze the
mineral types in the panned heavy mineral fraction and to calculate their volumetric percentages. Data
were analyzed using Gradistat™ 4.0 software. Results revealed that llmenite, Rutile, Zircon and the Garnet
were the dominant heavy minerals in the northeast coast and the Mahaweli River sediments. Further,
results revealed that heavy mineral assemblage of Mahaweli River sediments and Verugal deposit are
more or less similar in heavy mineral composition in contrast to Pulmoddai deposit. These results
support Mahaweli River sediments, mainly transport its sentiments towards the Verugal deposit.
