Guano

Synonym

Phosphorite, Aluminium phosphate, Alumino-phosphate

Required Geological Setting

Neogene and Quaternary sediments, Paleogene and older sediments

Occurrence

Phosphate dominant material originated from biological bodies accumulated for several to tens thousand years. The guano in a strict sense is observed in oceanic islands and is originated from excrements and carcasses of seabirds, and the bat guano is observed in caves and is originated from excrements and carcasses of bats. Guano in other geological circumstances is very rare as weathering rate is higher than accumulation rate of guano. Original guano contains large amount of nitrogen, and phosphate is more concentrated in regions of high rainfall as nitrogen is soluble in water. Guano may react with calcite to form calcium-phosphate mineralas such as hydroxylapatite on coral reefs of oceanic islands and limestone caves. The guano on coral reefs is a possible origin of phosphate-rich limestones reported from Neogene strata in the Japan island.

Reported Minerals

• Hydroxylapatite
• Brushite
• Taranakite