natural resources

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Across
  1. 2. constitutes up to 21% of the earth
  2. 5. gas constitutes up to 90% of Venus and mars
  3. 7. also found in urea and alkaloids
  4. 8. outermost layer of the earth
Down
  1. 1. one of the expensive metal
  2. 3. constitutes up to 78% of the earth
  3. 4. helps in preventing soil erosion
  4. 5. hardest metal in the world
  5. 6. core innermost layer of the earth