Geoscience Reference
In-Depth Information
number of natural mineral counterpart. Conversely, synthetic counterparts of many
zeolite minerals are not yet known. In recent years, some minerals having zeolite
structure have been reported; one such example is cavansite, Ca(VO) (Si
4
O
10
)
4H
2
O, which was reported by Staples et al.
[32]
, from cavities and veinlets in
basalts and tuffs in Oregon, USA. Its crystal structure was reported by Evans
[33,34]
. Subsequently, this mineral was reported from several other localities.
Powar and Byrappa
[35]
have reported cavansite from India and they have carried
out detailed X-ray, thermal, and infrared studies. The paragenesis of the mineral
cavansite is closer to zeolites. It has a 3D/vanadosilicate network analogous to gis-
mondine. However, based on a detailed infrared spectroscopic study, it was found
that in cavansite, water molecules occur both as loosely held and as tightly bound
crystal water
[35]
. Thus, the possibility of the existence of such new minerals hav-
ing the structures of zeolites cannot be ruled out.
In recent years, the compositional
structural range of molecular sieves have
been significantly increased by the discovery of crystalline microporous
aluminophosphate-based frameworks, beginning with the aluminophosphates or
AlPO
4
-n molecular sieves, followed by silicoaluminophosphates, titanium alumi-
nophosphates, metal aluminophosphates, and metal silicophosphates, designated
as SAPO-n, TAPO-n,MeAPO-n, and MeAPSO-n, respectively.
In 1961, d'Yvoire
[36]
reported the synthesis of several aluminophosphate
hydrates such as H
1
,H
2
,H
3
, and H
4
. These materials were prepared from dilute
aqueous solutions of alumina and phosphoric acid with a P
2
O
5
:Al
2
O
3
ratio of 2.7.
Much of the success in the laboratory synthesis has been achieved by duplicating
the conditions under which natural zeolites were produced. In nature, water plays a
key role in the crystallization of zeolites, whereas in the laboratory the zeolites'
structure formation insists on the presence of the organic molecules.
Tables 6.6
6.8
Table 6.6 Synthetic Counterparts of Natural Zeolites—Alkaline Metal
[37]
Zeolite
Alkali
Investigator
Date
Mordentie
Na
R.M. Barrer
1948
Analcime
Na
R.M. Barrer
1949
Phillipsite
Na
R.M. Barrer
1951
Cancrinite
Na
R.M. Barrer
1952
Natrolite
Na
R.M. Barrer
1952
Faujasite
Na
R.M. Milton
1956
Gmelinite
Na
R.M. Barrer
1959
Chabazite
Na
R.M. Milton
1960
Erionite
K, Na
D.W. Breck
1960
Clinoptilolite
Li
L.L. Ames, Jr.
1963
Ferrierite
Na
E.E. Senderov
1963
Gismondine
Na
A.M. Taylor
and R. Roy
1964
Bikitalite
Li
D.J. Drysdale
1971
Edingtonite
K
R.M. Barrer
1974
