好肥一棵树 发表于 2011-12-16 20:52 
楼主学什么的,是学岩土工程方面的么?
还有把上下文也发出来看看呗
Calcium orthophosphates are abundant in both nature
and living organisms. Geologically, natural calcium
orthophosphates are found in different regions mostly
as deposits of apatites (mainly as natural fluorapatite
(FA), chemical formula Ca10(PO4)6F2) or phosphorites
[8, 11]. The chemical composition of the latter cannot
be described so easily. As phosphorites belong tosedimentary deposits, their general appearance and the
chemical composition vary a lot. It is a common
practice to consider francolite (or carbonate-hydroxyfluorapatite
regarded as its synonym) as the basic
phosphorite mineral [11–15]. A cryptocrystalline (almost
amorphous) variety of francolite (partly of a
biological origin) is called collophane (synonyms:
collophanit, collophanita, collophanite, grodnolite,
kollophan) [16]. It occurs in natural phosphorites
predominantly as fossil bones and phosphatized microbial
pseudomorphs: phosphatic crusts of chasmolithic
biofilms (or microstromatolites) and globular clusters
with intra-particular porosities [17]. Natural phosphorites
(therefore, francolite and collophane as well)
occur in various forms, such as nodules, crystals, or
masses. The world deposits of natural calcium orthophosphates
are estimated to exceed 150 billion tons;
from which approximately 85% belong to phosphorites
and the remaining 15% belong to apatites [18]. |