Mineral matter

The minerals are extremely variable in size. Some are as large as the smaller rock fragments; others, such as colloidal clay particles, are so small that they cannot be seen without the aid of an electron microscope. Quartz and some other primary minerals (biotite, muscovite etc.) have persisted with little change in composition from the original rock. In general, the primary minerals dominate the coarser fractions of soil. Secondary minerals (silicate clay, limonite, haematite etc.) are prominent in the fine materials, especially in clays. Clearly, mineral particle size do much effect on the properties of soil.