Which one of the following sedimentary rocks has <strong>NOT</strong> been formed mechanically?

  1. A. Sandstone
  2. B. Conglomerate
  3. C. Loess
  4. D. Geyserites

Correct Answer: D. Geyserites

Explanation

Geyserites are a form of opaline silica that precipitates chemically from the hot water of geysers and hot springs, making them chemically formed sedimentary rocks, unlike mechanically formed sandstone, conglomerate, and loess.

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