Dear Mrs. Giron:

Collophane is a mineralogical term used for the cryptocrystalline or massive carbonate-apatite, also known as francolite or dahllite [Ca5 (PO4, CO3)3(OH, F)] which is the most common constituent in sedimentary phosphate deposits (phosphorites). All kinds of alteration such as decomposition on decreasing pH and transformation into Al-P-Sulfate minerals may also be observed similar to F-apatite during weathering of collophane. The term amorphous applied to this phosphate is misleading since these minerals also provide diagnostic diffraction lines as being x-rayed.

Dill, H.G. and Kantor, W. (1997) Depositional environment, chemical facies and a tentative classification of some selected phosphate accumulations.- Geologisches Jahrbuch,  D 105: 3-43.

Cordiales saludos

Harald G. Dill

thank you very much for your help, the truth is that in my project I met with many variations colophane (color, texture, relief) at the microscopic level and have been looking for information but can not find, if you. know some text that can guide me appreciate him.

Collophane is massive, cryptocrystalline, variety of Carbonate-rich Fluorapatite or Carbonate-rich Hydroxyl apatite, constitute the bulk of phosphate rock and fossil bone.

The weathering pattern will be similar to that of apatite, that represents the major source of phosphorus for biological processes, sediments, and soils.

carbonate-fluorapatite with clay produce Ca(Na, K)-Al-phosphate and Al- or Fe-phosphate minerals, the compositions of which depended on the chemistry of the parent rock and degree of weathering.

Acid conditions and the absence of carbonates in rocks promote the breakdown

of apatite, often leading to the formation of Fe- and Al-phosphates.

Ca5(PO4,CO3)3(OH)