[en] Posiva Oy has acquired an extensive amount of data on the geology of the Olkiluoto Island. Part of that data is the collection of foliation information, known as the foliation database. In this work, the foliation database was studied and analyzed using data mining techniques aiming to characterize the properties of the database. The goal was to discover previously unknown correlations, patterns, and properties contained within the data. In addition to the foliation database, deviation survey measurements were used as a supporting dataset. The following analyses related to the general properties of the database were carried out: logical discrepancies and potential errors in data; statistics of alphanumeric strings, numeric values, and empty fields; discovery of stereotypic data items whose appearance count deviates significantly from the count that would be expected if the properties were assumed independent; analysis of free text remarks; comparison between reported foliation orientations with those that were recalculated using the core orientations and foliation orientations with respect to core. Rock and foliation type sequences were analysed both in terms of the lengths of contiguous segments and the frequencies in which different sequences appear in the drillholes. The variance of rock types and the density of measurements was assessed by dividing the bedrock volume of interest into cubes and providing numerical values for these quantities for each cube. This was carried out in two resolutions: cube's sides were 500 m and 200 m. The foliation orientations were summarized also with respect to these cubes. In addition to analysis tasks, another task was to come up with alternative bedrock models - in terms of rock type units - based on data that contains rock type classifications and foliation orientation measurements obtained from drillholes. The interpretation of the analysis results was beyond the scope of this work. The assessment of the novelty and the usefulness of the discovered patterns and relationships requires domain expertise and familiarity with the everyday practices on how the data is utilized, what assumptions are satisfied and which aspects are significant. Instead, this report gives numerous different viewpoints on the data and through them, brings up issues that might require further investigation or just verifies the current conception of issues related to the geology of Olkiluoto Island. (orig.)