DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: HS193
MINERAL_TYPE: Tectosilicate
MINERAL: Chabazite (Zeolite group)
FORMULA: CaAl2Si4012*6H2O
FORMULA_HTML: CaAl2Si4012•6H2O
COLLECTION_LOCALITY: Colorado
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
SAMPLE_DESCRIPTION:
Usually found in rhombohedral chrystals, with nearly cubic angles. The ideal composition listed in the FORMULA field often has considerable replacement of Ca by Na and K as well as (Na,K)Si for CaAl. The structure of chabazite consists of an Al-Si-O framework with large cagelike openings bounded by rings of tetrahedra. The cages are connected to each other by channels which allow diffusion of molecules of less than ~3.9 Angstroms.
The bands seen in its near-infrared spectrum are typical of large quantities of molecular water.
See: Hunt, G.R., J.W. Salisbury, 1970, Visible and near-infrared spectra of minerals and rocks: I. Silicate minerals. Modern Geology, v. 1, p. 283-300.
END_SAMPLE_DESCRIPTION.
XRD_ANALYSIS:
40 kV - 30 mA, 6.5-9.5 keV
File: chab193.out, -.mdi; chabz193.out, -.mdi
References: JCPDS # 34-137, 35-498, 42-1451
Found: Chabazite, thomasite, wairaikite in subequal proportions
Comment: Reflections are sharp and strong, suggesting good crystallinity and compositional homogeneity. Many peak overlaps made interpretation of the pattern very difficult. Consideration of the relative intensities of chabazite and thomasite led to the realization that some sharp peakshad an intensity contribution from a third phase, which turned out to be wairaikite.
J.S.Huebner, J. Pickrell, T. Schaefer, written communication(USGS 1994)
END_XRD_ANALYSIS.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
COMPOSITION_DISCUSSION:
None
END_COMPOSITION_DISCUSSION.
MICROSCOPIC_EXAMINATION:
96 vol% Chabazite
2 vol% other phases including magnetite
2 vol% Fe-stained grains
av gr sz = 275µm
Clear grains, fibrous prismatic cones, low birefringence, very small 2V which is charateristic of the Chabazite group. G. Swayze
END_MICROSCOPIC_EXAMINATION.
SPECTROSCOPIC_DISCUSSION:
END_SPECTROSCOPIC_DISCUSSION.
SPECTRAL_PURITY: 1_2_3_4_
LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment
LIB_SPECTRA: splib04a r 884 0.2-3.0µm 200 g.s.= 275µm
LIB_SPECTRA: splib05a r ____ 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=