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TITLE: Smaragdite HS290 Amphibole DESCRIPT
DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: HS290
MINERAL_TYPE: Inosilicate
MINERAL: Smaragdite (Actinolitic Amphibole)
FORMULA: Ca2(Mg,Fe+2)5Si8O22(OH)2 (see sample description)
FORMULA_HTML: Ca2(Mg,Fe+2)5Si8O22(OH)2
COLLECTION_LOCALITY: Clay County, North Carolina
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
SAMPLE_DESCRIPTION:
The general formula for members of the amphibole group is W0-1X2Y5Z8O22(OH,F)2, where W represents Na and K in the A site, X denotes Ca+2, Na+, Mn+2, Fe+2, Mg+2, and Li+ in the M4 sites, Y represents Mn+2, Fe+2, Mg+2, Fe+3, Al+3, and Ti+4 in the M1, M2 and M3 sites and Z refers to Si+4 and Al +3 in the tetrahedral sites. This sample's composition is probably similar to ferroactinolite, Ca2(Fe+2,Mg)5Si8O22(OH)2.
"I-16 Smaragdite 290B--Clay Co., N. Carolina: Smaragdite is also a name sometimes given to actinolitic amphibole derived from pyroxene by alteration. Like uralite, it typically contains Al, for which Fe3 can substitute. This sample shows both ferrous and ferric iron bands at 1.0µ and 0.7µ in its spectrum, as well as the hydroxyl features at 1.4, 2.32, and 2.38µ. Other weaker features between 2.1 and 2.3µ are hydroxyl-lattice combination bands. Some included water is again indicated by the band at 1.9µ."
Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1973, Visible and near-infrared spectra of minerals and rocks: VI. Additional silicates. Modern Geology, v. 4, p. 85-106.
END_SAMPLE_DESCRIPTION.
XRD_ANALYSIS:
40 kV - 30 mA, 6.5-9.5 keV
File: smarg290.mdi
References: Huebner's reference patterns; Hawthorne (1981); Borg and Smith (1969); JCPDS #45-1342, 23-1405, 44-1402, 41-1366
Found: Calcic amphibole, plagioclase feldspar, unidentified minor phase(s)
Sought but not found: beryl
Comments: Peaks are sharp, symmetric, and show good resolution of alpha1-alpha2 components. Given the quality of the pattern, it is unusual that the interpretation is so indefinite. After indexing following Borg and Smith (1969), the following amphibole unit cell dimensions were obtained: a=9.792(7), b=17.944(24), c=5.289(4) angstroms, and beta=104.93(7) degrees. These values suggest that the M4 site is occupied by Ca or Ca+Na, excluding the Mg-Fe and sodic amphibole groups (Hawthorne, 1981, fig. 43). Line-based search-match returned six amphiboles (including magnesioriebeckite, a sodic amphibole) and three plagioclases. Profile-based search match returned kaersutite (44-1450) and anorthite (44-1481). Search on the refined cell dimensions returned many amphiboles. By overlay of PDF2 patterns on the HS290 pattern, kaersutite (44-1450), edenite (23-1405) and K-pargasite (39-0373) matched the amphibole phase and albite (41-1480) and anorthite (41-1481) matched the feldspar. Eleven moderate to weak reflections (7.4, 5.40, 5.03, 3.52, 1.881, 1.804, 1.641, 1.629, 1.578, 1.433, and 1.358 angstroms) have not been identified, using the PDF2 minerals file.
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