The size, shape, and composition of coherent nanostructures in hydrocarbon resources from natural gas to bitumen continue to be debated. Much research has focused on asphaltenes and other fractions separated chemically from their underlying hydrocarbon resources and their behaviors exhibited when these materials are remixed or added to other fluids. In this contribution, we step back and pose a simple question: "what can be learned about nanostructure size and composition in hydrocarbon resources using a simple physical separation technique?" To this end, Athabasca bitumen and Maya crude oil were partitioned, without solvent addition, using nanofilters at 473 K. These feeds possess significant asphaltene contents and, in the case of Athabasca bitumen, significant mineral matter content, which facilitate the measurement and interpretation of standard chemical analyses obtained for the feeds, and for permeates and retentates produced. Organic and inorganic elemental composition and saturate, aromatic, resin, and asphaltene fractions were obtained. Details of the experimental and analytical techniques employed and their limitations are presented. Pentane asphaltene-enriched nanostructures, and mineral-matter-rich nanostructures, with distinct size distributions, and independent behaviors are identified. The asphaitene-rich nanostructures are shown to possess a broad size distribution, and they do not associate preferentially with other constituents such as resins. Implications of these key results are discussed.