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J.A. Konnert

Publications and source records attributed to J.A. Konnert.

6 recordsLinked to original sources
USGS2000

The crystal structure of tetranatrolite from Mont Saint-Hilaire, Quebec, and its chemical and structural relationship to paranatrolite and gonnardite

The structure of tetranatrolite from Mont Saint-Hilaire, Quebec (U.S. National Museum sample R1830) with a = 13.197(7) A, c = 6.630(9) A, and space group I42d, was refined using single-crystal X-ray data. A representative formula of tetranatrolite determined from electron microprobe analysis is Na12.50K0.01Ca2.93Sr0.11Al19.09 Si20.91O79.74??nH2O. The structure has the basic natrolite Si-Al-O framework configuration with Na, Ca, Sr, and K residing within inter-framework cages. Aluminum is disordered over the T1 and T2 tetrahedral sites, with T2 > T1. Water molecules O4 and O5 coordinate the intercage atoms and have high displacement parameters, indicating disorder within the cages. The Mont Saint-Hilaire tetranatrolite structure is compared to four previously determined structures, two tetranatrolite samples from Khibiny and Lovozero, Russia and two "gonnardite" samples from Tvedalen, Norway and Gignat, France. Observations are given to indicate that the Norwegian sample deduced to be tetranatrolite rather than gonnardite. Although the crystal structures of tetranatrolite and gonnardite are very similar, it is shown that the tetranatrolite compositions differ significantly from those of gonnardite. The tetranatrolite composition series varies along the join Na16Al16Si24O80-Na12 Ca4Al20Si20O80, and is represented by the formula Na16-xCaxAl16+xSi24-x O80??nH2O, where x extends from approximately 2.4 to 3.9. In contrast, gonnardites from Arkansas and Austria have compositions that vary along the join Na16Al16Si24O80-Na4 Ca8Al20Si20O80, which are represented by the formula ???xNa16-3xCa2xAl16+x Si24-xO80??nH2O and where ??? indicates vacant intercage cation sites and x varies from approximately 0.3 to 3.2. Tetranatrolite is a dehydration product of paranatrolite and probably does not have a true stability field.

American Mineralogist↗
USGS1989

Mineralogical studies of the nitrate deposits of Chile: VI. Hectorfloresite, Na9(IO3)(SO4)4, a new saline mineral

The new mineral hectorfloresite, known to occur in only one locality in the nitrate fields of northern Chile, consists of tiny prismatic crystals, generally less than 1 mm long and 0.2 mm in diameter, in cavities in dense nitrate ore consisting of saline-cemented silt, sand, and small rock fragments. The physical, optical and crystallographic properties of the new mineral are described. -from Authors

American Mineralogist↗
USGS1987

Crystal structure and crystal chemistry of melanovanadite, a natural vanadium bronze.

The crystal structure of melanovanadite from Minas Ragra, Peru, has been determined in space group P1. The triclinic unit cell (non-standard) has a 6.360(2), b 18.090(9), c 6.276(2) A, alpha 110.18(4)o, beta 101.62(3)o, gamma 82.86(4)o. A subcell with b' = b/2 was found by crystal-structure analysis to contain CaV4O10.5H2O. The subcell has a layer structure in which the vanadate sheet consists of corner-shared tetrahedral VO4 and double square-pyramidal V2O8 groups, similar to that previously found in synthetic CsV2O5. Refinement of the full structure (R = 0.056) showed that the Ca atom, which half-occupies a general position in the subcell, is 90% ordered at one of these sites in the whole unit cell. Bond length-bond strength estimates indicate that the tetrahedra contain V5+, and the square pyramids, V4+.-J.A.Z.

American Mineralogist↗
USGS1978

The crystal structure and thermal history of orthopyroxene from lunar anorthosite 15415

A single crystal of untwinned orthopyroxene from lunar anorthosite sample 15415, with composition (Mg 1.14 Fe 0.80 Mn 0.02 Ca 0.04 )(Si 1.97 Al 0.03 )O 6 , has a unit cell in space group Pbca with a = 18.310(15)Å, b = 8.904(10)Å, c = 5.214(7)Å, containing 2 formula units. A set of 742 counter-measured intensity data made with MoK α radiation has been used to refine the crystal structure in isotropic thermal mode to R = 0.116. Anisotropic refinement led to R = 0.092, but thermal parameters are distorted by non-random errors resulting from poor crystal texture. The resulting structure is in close agreement with that obtained by Ghose [9] for a hypersthene from Greenland. A parameter q , which gives ( Mg q Fe 1−q ) for cation site M (1) and (Mg 1.14− q Fe q −0.18 Ca 0.04 ) for site M (2), was included in the least-squares analysis, yielding q = 0.90(1). This orthopyroxene has the high degree of cation order expected of pyroxenes subjected to Apollonian metamorphism at lower than 500–600°C. No evidence exists for a subsequent thermal event of sufficient intensity to disorder the pyroxene. On the basis of previous laboratory studies of argon-release patterns of lunar plagioclase and order-disorder kinetics of terrestrial pyroxenes, we attribute the reported isotopic age (3.9–4.1 AE) to cessation of metamorphism, perhaps caused by impact excavation.

Earth and Planetary Science Letters↗