Clay mica - mica must be present in initial parent material. Moderate pH and concentrations of Si and Al. Gives soil a yellow color. Variable moisture conditions, but weathers to hematite under high oxidizing conditions. Hematite - Fe 2 O 3 .
Gives soil a red color.
Can form under variable moisture conditions but is favored under high oxidizing conditions. Found in poorly drained soil. Requires low oxygen content and reducing conditions. Has a bright yellowish orange color. Gibbsite - low Si concentration and acid pH. Intense weathering conditions.