text: This section lists only historical data. For recent data, see Abundance of elements in Earth's crust.
  Technical definition of "clarke", "Earth's crust" and "lithosphere" differ among authors, and the actual numbers vary accordingly, sometimes by several times. Even the same author presents multiple versions, with various estimation parameters or knowledge refinements. Yet they are often quoted without source, rendering the data unverifiable.
  Clarke & Washington presented estimations of the average composition of outer part of Earth with four variants:
  # 10-mile crust, hydrosphere and atmosphere.
  # 20-mile crust, hydrosphere and atmosphere.
  # 10-mile crust, only igneous rocks and sedimentary rocks. (i.e. exclude hydrosphere and atmosphere)
  # 10-mile crust, only igneous rocks. (i.e. exclude hydrosphere and atmosphere)
  "The earth's crust" in Clarke and Washington works can mean two different things: (a) The whole outer part of Earth, ie. lithosphere, hydrosphere and atmosphere; (b) Only the lithosphere, which in their works just meant "the rocky crust of the earth". "Crust" here means (b).
  * Following tables do not cover all elements. Some elements not on the table may have larger abundance. Some minor elements are listed here to aid identifying the origin of unsourced documents.
  * Some entries contain data for the disputed element 43 masurium.
  * Precision (number of digits) may be adjusted to improve legibility.