From bluestem@webserf.net Wed Nov 24 17:51:00 1999 Date: Wed, 24 Nov 1999 20:00:04 From: Bluestem Associates To: "sanet-mg@ces.ncsu.edu" Subject: Phosphate rock On Wed, 24 Nov 1999 14:15:26 -0500 (EST), Lawrence F. London, Jr. wrote: >Black Rock Phosphate" this mined product is rated at the top of the list. >It is black in color and is shipped out, with minimal processing, in >exactly the condition it is in when excavated, as a fine sand. PCS used to >grind it to a powder but found that that did not speed release The primary factor in the 'release' of rock phosphates is the amount of carbonate they contain as a structural substitution in the non-phosphate anionic section of the apatite-group minerals comprising most of the rock. The more carbonate, the more easily available. Moroccan phosphates (the best in the world) often contain 5% carbonate (or even more), making them readily available in acid soils. Hard-rock phosphates are typically tricalcium phosphates with no carbonate, and as a result they take just about forever to release. Text-based systems aren't very good for chemical formulae, but if you take all numbers as chemical subscripts the following is the general formula for generic apatites. Ca2Ca3[PO4]3(OH,F,CO3) is the simple version. For you real keeners out there, the more detailed formula is for an apatite-group mineral called francolite, itself a common component of many of the best phosphate rocks. Ca4Ca6[PO4]6-x(CO3)x(F,OH)2+x Phosphate mineralogy is an absolute blast, and if anyone wants more information they should contact me off list. Bart To Unsubscribe: Email majordomo@ces.ncsu.edu with the command "unsubscribe sanet-mg". If you receive the digest format, use the command "unsubscribe sanet-mg-digest". To Subscribe to Digest: Email majordomo@ces.ncsu.edu with the command "subscribe sanet-mg-digest". All messages to sanet-mg are archived at: http://www.sare.org/san/htdocs/hypermail