A search has been performed for possible commercial grade diatomaceous silica - rich sediments within an area straddling the Greanium - Lameroo - Pinnaroo Road and extending westwards from the SA/Vic. state border for ~90 km. The target locations were north-westerly orientated hollows in topography that were expected to contain such types of lacustrine or lagoonal sediments. During previous SA Government geological mapping of the PINNAROO 1:250k mapsheet area (P. Rogers, 1980), diatomite >0.5 m thick was discovered in a road rubble borrow pit situated 6.5 km north of Parrakie in the Murray Mallee. Following a review made of regional drillhole and water bore geological logs, and a field inspection of a large area of the SA Murray Mallee conducted during February-March 1991, concentrating on road cuttings and other council - made excavations, plus many farm dams, it was found that diatomite is exposed at only two sites located about 10 km apart: the aforesaid 'Parrakie rubble pit' in the Lameroo district, and the 'Mintabie [Farm gateway] rubble pit in the Karoonda district. The licensee next commissioned a photogeomorphic study from expert consultants to try to delineate possible elongate hollows in the top of Pliocene Parilla sand that might have been suitable sites for diatomite accumulation in playa environments. Identified hollows were later inspected during August 1991. Laboratory petrographic and palaeontological examinations were made on samples collected from the Parrakie and Mintabie occurrences, which confirmed their siliceous fossil nature and gave indicative abundances of diatoms and sponge spicules in the sediments. Several large blocks of rock from the Parrakie pit were sent to Commercial Minerals Ltd for crushing, calcining and absorption tests. The absorbency values were only moderate, well below but approaching that of imported products. During March-April 1992, 23 shallow vertical RC aircore holes totalling 146.9 m were drilled at selected favourable sites (the borrow pits, near to two water wells with anomalous near surface strata, and in inferred palaeolagoons) to scout for the highest quality diatomite and with the (unrealised) intent of providing short lengths of core of indurated rock to undergo further testing. This work largely proved to be disappointing, although it did disclose a further small deposit 14 km north of Geranium Siding. However, no diatomite was found by drilling in the interdunal hollows.