Conclusions

1. Soil organic matter occurred in aggregates and as separate particles. When found in aggregates, organic materials did not appear to be the principle aggregating agent.
2. Persistent aggregates frequently contained abundant iron oxides.
3. Quartz was the major mineral in both the sand and silt fractions (about 70% of the silt by grain count). It occurred in a variety of shapes, well rounded grains from Coastal Plains sediments, slightly rounded hexagonal polyhedra from crystalline rock parent materials, with abundant overgrowths on primary grains in a young soil formed in Mississippi River alluvium, and grains coated with iron oxides from several soils including the Marlton.
4. Feldspars have obvious structurally controlled weathering patterns of cavities and grooves.
5. Fossils from carbonatic parent material of a Vertisol from Oklahoma retained general features of the original organisms sometimes with drusy surfaces.
6. Even the Oxisol from Puerto Rico contained weatherable minerals (serpentine).
7. The complex assortment of aggregates, porous grains and odd shapes coupled with the wide assortment of minerals make the need for real data on soils to predict their chemical and physical behavior increasingly evident.