although I have not performed any determination of lattice parameters of laumontite, maybe the papers may be of help for you:
Please find some information on laumontite and zeolites.
Zeolites in ophiolites:
DILL, H.G., FUESSL, M. and BOTZ, R. (2007) Mineralogy and (economic) geology of zeolite-carbonate mineralization in basic igneous rocks of the Troodos Complex, Cyprus.-Neues Jahrbuch für Mineralogie Abhandlungen, 183: 251-268.
Zeolite deposits worldwide:
DILL, H.G. (2010) The “chessboard” classification scheme of mineral deposits: Mineralogy and geology from aluminum to zirconium.- Earth Science Reviews, 100: 1-420.
Zeolites in subaerial tuffs:
DILL, H.G., TECHMER, A., BOTZ, R., DOHRMANN, R. and KAUFHOLD, S. (2012) Hypogene and supergene alteration of the zeolite-bearing pyroclastic deposits at Tell Rimah, Jordan, and rift-related processes along the Dead-Sea-Transform Fault System during the Quaternary.- Journal of Volcanology and Geothermal Research, 239-240: 49-68.
Zeolites in alluvial-fluvial-lacustrine sediments:
DILL, H.G., KAUFHOLD, S., LINDENMAIER, F., DOHRMANN, R., LUDWIG, R. and BOTZ, R. (2012) Joint clay-heavy-light mineral analysis: A tool to investigate the hydrographic-hydraulic regime of the Late Cenozoic deltaic inland fans under changing climatic conditions (Cuvelai-Etosha Basin, Namibia).- International Journal of Earth Sciences, 102: 265-304.
See further literature cited therein.Maybe it is of help for you for the moment.
I recommend the website of the structure commission of the International Zeolite Association as a starting point:
http://izasc.ethz.ch/fmi/xsl/IZA-SC/ft.xsl
Here, you can find information about the framework connectivity etc., and a model of a hypothetical all-silica laumontite (Laumontite has LAU topology).
The IZA commision on natural zeolites also maintains a website with information on laumontite, with lots of references to previous structural studies:
The ICSD contains tens of structure descriptions of Laumontite, incl. lattice parameters of course, but also the free AMCSD (American Mineralogist Crystal Structure Database) lists around 16 descriptions of this mineral.
Yes. Many investigators have determined. I agree with the suggestions of Professor Dr Gert Nolze. There may be slight difference in the vales of the lattice parameters , depends on the impurity level. Laumontite is a thoroughly studied zeolite as it is the upper limit of zeolite facies metamorphism.