Larsen, A. O. 1981: Boehmite
from syenite pegmatites in the Oslo Region, Norway. Mineralogical Record,
12, 227-230.
Well developed crystals of colourless
to pale brown boehmite have been found in the Saga I and II quarries in
the Tvedalen area, Norway. The mineral occurs as flattened dipyramidal
crystals up to 1 mm in length, usually in intergrown aggregates, in vugs
in fibrous natrolite, together with a large suite of accessory minerals.
The following forms have been observed: {010}, {011}, {210} and {111}.
The Saga I boehmite is biaxial (+), 2Vz = 74(3)º,
and the refractive indices are alpha = 1.644(2), beta = 1.654(2) and gamma
= 1.664(2). The unit cell dimensions for tha Saga I boehmite are a
= 3.687(9), b = 12.226(9), c = 2.866(2) Å and V
= 129.2 Å3. The boehmite is close to pure AlO(OH) with
only minor substitution of Si, Ti, Fe, Ga, Mn and Ca for Al. Boehmite and
the associated Al-hydrates diaspore and gibbsite represent the final product
of decomposition of nepheline during a late, low temperature hydrothermal
stage of the pegmatite formation.
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Larsen, A. O. 1988: Helvite
group minerals from syenite pegmatites in the Oslo Region, Norway. Contribution
to the mineralogy of Norway, No. 68. Norsk Geologisk Tidsskrift, 68,
119-124.
Most helvite group minerals from
the syenite pegmatites in the Oslo Region are manganese rich with helvite
mol% ranging from 65% to 98.5%. From the present investigation of sixteen
helvite group minerals, only two fall in the genthelvite field of the helvite-danalite-genthelvite
triangular composition diagram. Yellow helvite (98-98.5 mol% helvite) from
the Saga I quarry at Mørje, Porsgrunn, and a very pale green genthelvite
(98 mol% genthelvite) from Bratthagen in Lågendalen are among the
purest helvite group members hitherto reported. The Saga and Sandøy
helvites are the first examples of fluorescence among the manganese rich
helvites.
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Larsen, A. O. 1989: Senaite
from syenite pegmatite at Tvedalen in the southern part of the Oslo Region,
Norway. Norsk Geologisk Tidsskrift, 69, 235-238.
Senaite, the plumboan member of
the chrichtonite group, has been found in a syenite pegmatite in a larvikite
quarry at Bjørndalen in the Tvedalen area in the southern part of
the Oslo Region. Senaite occurs as well-formed interpenetration twins up
to 4x1 mm large with c as the twin axis. The colour is black with a submetallic
adamantine lustre. The streak is greenish black. The density is 4.96(1)
g/cm3 (measured) and 4.93 g/cm3 (calculated). The
unit cell dimensions are (trigonal, space group R3) a = 10.418(1),
c
= 20.928(2) Å and V = 167.1(3) Å3. Chemical
analysis yields the structural formula Pb1.13(Ti13.66Fe(III)3.44Fe(II)1.22Zn1.87Mn0.55Y0.26Nb0.15)O38
which is in close agreement with the general formula AM21O38.
Crystallization of senaite, which contains the chalcophile elements Pb
and Zn, requires a hydrothermal fluid with an extremely low H2S
fugacity, typically found in syenites, alkali granites and certain hydrothermal
veins.
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Larsen, A. O. 1995: Identiteten
til de sorte amfibolene fra Oslo-feltets syenittpegmatitter. Norsk Bergverksmuseums
Skriftserie, 9, 27-34.
(The identity of the black amphiboles from the syenite pegmatites in the Oslo Region)
"Barkevikite" was introduced by Brøgger (1887, 1890) as the term for a black amphibole which often occurs as a major mineral in the syenite pegmatites in the Oslo Region, Norway. The name was adopted from the area where the mineral is abundant: Barkevik, 2 km north of Helgeroa in Brunlanes, Larvik. However, IMA Subcommittee on Amphiboles has discredited "barkevikite" as a valid mineral name (Leake 1978). In order to confirm the correct nomenclature for "barkevikite" and other amphiboles from the syenite pegmatites, 28 amphiboles have been analysed and classified.
After the article above was published, a revision of the nomenclature for amphiboles was given by Leake (1997). Subsequently, a revision of the same amphiboles from the syenite pegmatites in the Oslo Region as given above, was re-classified by Larsen (1998). The following general pattern can be reported: The traditional "barkevikite" from the Barkevik area is ferro-edenite, and most amphiboles in the Langesundfjord-Tvedalen district are ferro-edenites. Amphiboles from the area Hallevannet - Larvik - Tjølling are either magnesiohastingsites or hastingsites. Amphiboles from Vesterøya, Sandefjord are magnesiokatophorites.
Larsen, A. O. 1998: Revisjon av
nomenklatur for de sorte amfibolene fra Oslofeltets syenittpegmatitter.
Norsk
Bergverksmuseums Skriftserie, 14, 9.
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Larsen, A. O. 1996: Rare earth
minerals from the syenite pegmatites in the Oslo Region, Norway. In
Jones, A. P., Wall, F. & Williams, C. T. (eds.): Rare Earth Minerals.
Chemistry, Origin and Ore Deposits, 151-166. Chapman & Hall, London,
Glasgow/Weinheim/New York/Tokyo/Melbourne/Madras.
The article is a review of all rare
earth minerals and rare earth bearing minerals from the syenite pegmatite
in the Oslo Region. The history of these minerals and the geology of the
area are briefly described. Then follows short descriptions of 22 rare
earth minerals: loparite, fergusonite, bastnäsite, parisite, calcio-ancylite,
ancylite, xenotime, monazite, cerite, britholite, tritomite, melanocerite,
gadolinite, hingganite, tadzhikite, mosandrite, chevkinite, perrierite,
allanite, cappelenite, stillwellite, kainosite, plus some remarks on minerals
in which rare earth elements play a subordinant role.
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Larsen, A O. 1996: Zirkondriften
på Stokkøya. Nesjar, 1995-1996, 57-59.
(The zircon prospect at the Stokkøy island)
The German war industry during the
Second World War was in constant need of raw materials, among others zircon.
A rich, zircon-bearing syenite pegmatite at the Stokkøya island
in the Langesundfjord district was described already by Brøgger
(1890), and this pegmatite dike was subject to exploitation by the German
interests in the autumn of 1942. Approximately 2.5 tons of zircon-bearing
pegmatite was shipped from the locality. Thus one of the classic localities
in the Langesundfjord was forever destroyed. The paper gives details about
the history.
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Larsen, A. O. 1998: Identiteten
til sorte glimmere i biotittserien fra syenittpegmatitter i Langesundsfjordområdet.
Norsk
Bergverksmuseums Skriftserie, 13, 5-8.
(The identity of black micas of the biotite series from the syenite pegmatites in the Langesundsfjord area)
"Lepidomelane" and biotite have
previously been used as names for the black micas from the syenite pegmatites
in the Oslo Region. Despite the fact that this mica is a main mineral in
most of the pegmatite dikes, no modern analyses have been reported on this
mineral. New chemical analysis on nine samples from the Langesundsfjord
area are reported in this paper. The results show that all the samples
are classified as annite, with a high content of Ti and Mn, low content
of Al and Fe3+, and a relatively narrow range of Mg/(Mg+Fe2+)
values. The micas contain 0.2% - 0.5% Li2O.
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Larsen, A. O. 2000: Brøgger
og Reusch: Den første turen til Langesundsfjorden. Norsk Bergverksmuseums
Skriftserie, 17, 35-38.
(Brøgger and Reusch: The first trip to the Langesundsfjord)
A the summer of 1873, the geology
students Waldemar Christopher Brøgger (age 22) and Hans Henrik Reusch
(age 21) went on their first excursion to the Fredriksvern (Stavern) and
Langesundsfjord district to collect minerals from the syenite pegmatites.
Brøgger's diary, in his own words, gives an interesting insight
into the life of two young students.
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Larsen, A. O. & Åsheim.
A. 1995: Leifite from a nepheline syenite pegmatite on Vesle Arøya
in the Langesundsfjord district, Oslo Region, Norway. Norsk Geologisk
Tidsskrift, 75, 243-246.
Leifite been found in a nepheline
syenite pegmatite on the southeastern part of the island Vesle Arøya
in the Langesundsfjord district, Norway. The mineral occurs as white to
colourless fibrous masses and radiating bundles. The unit cell dimensions
are a = 14.387(1) Å, c = 4.8734(7) Å and V
= 873.6(1) Å3. The mineral is uniaxial positive, eta = 1.521(1) and
omega = 1.517(1). Dmeas = 2.59(1) g/cm3. Dcalc = 2.60 g/cm3. IR spectroscopic
analysis shows that leifite contains (OH) groups, but no water of crystallization
as previously assumed. Wet chemical analysis gives the following empirical
formula: (Na6.14K0.92Cs0.04Mg0.03Ca0.01)Be2.07Al3.04Si14.61O37.99(OH)0.97F2.04.
The optical, physical and chemical data are in good agreement with previous
results for the mineral. New chemical data have also been obtained for
leifite from Narssarssuk, South Greenland.
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Larsen, A. O., Åsheim,
A. & Berge, S. A. 1987: Bromellite from syenite pegmatite, southern
Oslo Region, Norway. Canadian Mineralogist, 25, 425-428.
Bromellite has been found in a huge
syenite pegmatite dyke in the Saga larvikite quarry, Mørje, Porsgrunn,
in the southern Oslo region, Norway. The platy crystals, a few micrometer
thick and up to 0.1 mm across, form intergrown aggregates. The color is
white to creamy shite; the mineral fluoresces yellowish white in both long-vawe
and short-vawe UV light. Owing to the extremely thin crystals, only omega
(1.705(5)) could be measured. The unit cell is hexagonal, P63mc,
with a 2.697(4), c 4.372(4) Å and V 27.54(6)
Å3. A chemical analysis gave (in wt.%) SiO2
0.7, B2O3 1.4, Al2O3 1.2, Fe2O3
0.1, BeO 93.2, CaO 0.1, H2O 3.4, total 100.1. An infrared-absorption
spectrum shows that water forms an integral part of the structure. This
indicates that the Saga bromellite crystallized at about 200ºC in
vugs in coarsely crystalline natrolite, together with diaspore and chamosite,
during late-stage hydrothermal alteration of the primary minerals. Leucophanite
and Be-substituted nepheline (50 ppm Be) are possible sources for the beryllium
in the residual hydrothermal fluids from which the bromellite crystallized.
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Larsen, A. O., Åsheim,
A., Raade, G. & Taftø, J. 1992: Tvedalite, (Ca,Mn)4Be3Si6O17(OH)4·3H2O,
a new mineral from syenite pegmatite in the Oslo Region, Norway. American
Mineralogist, 77, 438-443.
Tvedalite occurs as cream white
to pale beige spherulites up to 3 mm in diameter in vugs in a nepheline
syenite pegmatite of the Vevja quarry in Tvedalen, Brunlanes, Vestfold
county, Norway. The tvedalite spherulites are always overgrown by a cryst
of chiavennite. Microprobe and wet chemical analyses as well as thermogravimetri
data give the chemical formula (Ca,Mn)4Be3Si6O17(OH)4·3H2O.
The realtive proportions of large divalent cations vary irregularly from
rim to core. The two most extreme compositions are (in percent of the non-Be
divalent atoms) Ca50Mn46Fe4 and Ca80Mn18Fe2.
Crystallographic data were obtained by a combination of X-ray powder and
electron diffraction methods. The mineral is orthorhombic, a = 8.724(6),
b
= 23.14(1), c = 4.923(4) Å, V = 993.8(9) Å3,
Z
= 2. The strongest reflektions (d in Å, (I/I0),
(hkl)) of the powder diffraction pattern are 11.6(93)(020), 5.80(68)(040,130),
3.87(75)(060), 3.16(74)(250,151), 2.889(75)(080,260,310), 2.837(100)(241),
2.494(58)(081,261). Cleavage is perfect (010), Dmeas
= 2.541(6) g/cm3, Dcalc = 2.554 g/cm3.
Mohs hardness is 4.5. The average refractive index is n = 1.604.
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Larsen, A. O. & Raade, G.
1991: Gaidonnayite from nepheline syenite pegmatite on Siktesøya
in the southern part of the Oslo Region, Norway. Norsk Geologisk
Tidsskrift, 71, 303-306.
Gaidonnayite, Na2ZrSi3O9·2H2O,
the orthorhombic dimorph of catapleiite, has been found in small vugs in
a nepheline syenite pegmatite on Siktesøya, Oslo Region, Norway.
The mineral occurs as transparent, colourless to very pale green crystals
in aggregates up to 1 mm across. Gaidonnayite probably formed as the result
of hydrothermal alteration of eudialyte. The crystals display the forms
{001}, {010}, {101} and {120}. The average of 18 electron microprobe analyses
gives the following empirical formula: (Na1.52K0.40)(Zr0.92Ti0.07Nb0.02)Si3.00O9·2H2O.
The unit cell dimensions are a = 11.761(8), b = 12.830(6),
c
= 6.693(4) Å and V = 1009.9(8) Å3. The cell
parameters of gaidonnayite show a linear correlation with the potassium
content. Gaidonnayite from Siktesøya shows a vivid green fluorescence
in short-wave UV light (254 nm). The UV excited fluorescence spectrum is
typical of uranyl-activated minerals.
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Larsen, A. O. & Raade, G.
1997: Pyroksener fra Oslofeltets syenittpegmatitter. Norsk Bergverksmuseums
Skriftserie, 12, 16-21.
(Pyroxenes from the syenite pegmatites of the Oslo Region)
Acmite and aegirine have been used
synonymously for more than 150 years. However, IMA CNMMN Subcommittee on
Pyroxenes has formally discredited acmite and accepted aegirine as the
correct name for the end-member NaFe3+Si2O6
among the Na-pyroxenes. Despite the fact that aegirine was first described
from the Langesundsfjord area, no modern analyses have been reported on
the pyroxenes from the syenite pegmatites of the Oslo Region. Chemical
analysis on 20 pyroxenes from 17 localities are reported in this paper.
Substitution mainly of the type (Ca.Mg.Mn.Fe2+) - (Na,Fe3+)
is very common. Some of the pyroxenes contain considerable amounts of the
divalent cations and are therefore classified as aegirine-augites, among
them "aegirine" from its type locality Låven. These are typically
magmatic pyroxenes. Green-coloured pyroxenes are aegirines of hydrothermal
origin. A significant amount of Sn is present in most of the pyroxenes,
highest in the hydrothermal aegirines. It is interesting to note that the
amount of Zr exceeds Ti in all of the XRF analysed samples.
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Larsen, A. O., Raade, G. &
Sæbø, P. C. 1992: Lorenzenite from the Bratthagen nepheline
syenite pegmatites, Lågendalen, Oslo Region, Norway. Norsk Geologisk
Tidsskrift, 72, 381-384.
Lorenzenite, Na2Ti2Si2O9,
from nepheline syenite pegmatites at Bratthagen, Lågendalen, Vestfold
county, Norway, occurs in two morphologically different habits: as well-developed
orthorhombic crystals or more rarely as fibrous aggregates. Crystal forms
observed: {100}, {210}, {111}, {211}, {321}. The unit cell dimensions for
Bratthagen lorenzenites are (coarsely crystalline/fibrous): a =
14.488(2)/14.480(1), b = 8.7061(11)/8.6995(8), c = 5.2308(8)/5.2277(3)
Å. Dmeas for coarsely crystalline lorenzenite is 3.436(1)
g/cm3. Coarsely crystalline lorenzenite is brown, while fibrous
lorenzenite is colourless to pale yellow. It is nonpleochroic, and strongly
birefringent. The axial dispersion is distinct r > v. Biaxial
negative, 2V = 42º±4º, n>1.80. The mineral shows
yellow fluorescence in short wave UV light. A cathodoluminescence spectrum
of coarsely crystalline lorenzenite shows an intrinsic type of luminescence
with a maximum at 500 nm. The average of seven electron microprobe analyses
gave the following results for coarsely crystalline/fibrous lorenzenite:
Na2O 17.13/17.74, SiO2 34.20/35.03, TiO2
44.39/45.13, FeO 0.83/0.34, Nb2O3 2.71/1.40, total
99.26/99.64. The average Fe:Nb ratios are 1:1.80/1:2.25, indicating substitution
according to the scheme Fe2+ + 2Nb5+ - 3Ti4+.
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Giuseppetti, G., Mazzi, F.,
Tadini, C., Larsen, A. O., Åsheim, A. & Raade, G. 1990: Berborite
polytypes. Neues Jahrbuch für Mineralogie, Abhandlungen, 162,
101-116.
Three polytypes of berborite, Be2(BO3)(OH)·H2O,
are described from nepheline syenite pegmatites of the Saga larvikite quarry,
Tvedalen district, southern Oslo region, Norway. Berborite-1T (similar
to type berborite from Pitkäranta, Karelian SSR) has space group P3;
cell parameters from single-crystal data are a = 4.434(1), c
= 5.334(2) Å. Its crystal structure was refined to R = 0.014. Berborite-2T
has space group P3c1; a = 4.431(1), c = 10.663(3)
Å; R = 0.019. The measured density is 2.06±0.01 g/cm3;
refractive indices are omega = 1.5817(3), eta = 1.4884(2) for 589 nm).
Berborite-2H has space group P63; a = 4.433(2),
c
= 10.638(5) Å, R = 0.029. Measured density 2.03 g/cm3;
omega = 1.5804(5), eta = 1.4928(2). The crystal morphologies of the three
polytypes are outlined. The 1T and 2T polytypes occur generally
as blocky crystals, often intergrown, while the 2H polytype occurs
as hexagonal, elongated prismatic crystals.Calculated and observed X-ray
powder data are given. It was found for all polytypes that the Be-atoms
and the O(2) apical oxygens of the Be-tetrahedra are split into two non-equivalent
sites. Water and hydroxyl oxygens are bordered on separate O(2) positions.
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Lumpkin, G. R., Colella, M.,
Smith, K. L., Mitchell, R. H. & Larsen, A. O. 1998: Chemical composition,
geochemical alteration, and radiation damage effects in natural perovskite.
In
McKinley, I. G. & McCombie C. (eds.): Scientific Basis for Nuclear
Waste Management XXI. Materials Research Society Symposium Proceedings,
506, 207-214.
Preliminary analytical and transmission
electron microscopy (AEM and TEM) results for a small suite of natural
perovskites are reported in this paper and discussed in relation to previous
work. We show that perovskite compositions in Synrock and tailored ceramics
plot within the known fields of natural perovskite compositions. AEM analyses
and electron diffraction work on selected samples indicate that they are
predominantly stoichiometric variants of the cubic perovskite structure.
Geochemical alteration was observed in one sample of loparite from Bratthagen,
Norway. The primary results of this alteration was leaching of Na from
the A-site. Although sufficient alpha-decay dose levels for complete amorphization
are not realized in this suite of samples, the available data bracket the
beginning of the crystalline-amorphous transformation at doses that are
~ 2-4 times greater than those of zirconolite of similar age. These results
may be due to fundamental differences in the damage annealing rates of
perovskite and zirconolite.
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Mazzi, F., Larsen, A. O., Gottardi,
G. & Galli, E. 1986: Gonnardite has the tetrahedral framework of natrolite:
experimental proof with a sample from Norway. Neues Jahrbuch für
Mineralogie, Monatshefte, 1986, 219-228.
The crystal structure of gonnardite
has been determined and refined (space group I-42d) on a
sample from a syenite pegmatite at the Vevja quarry, Tvedalen, Norway.
The tetrahedral framework is the same as for natrolite, but with a disordered
(Si,Al) distribution, like that currently assumed for tetranatrolite. There
is only one cation site, where Na is dominant over Ca. A review of gonnardite
and tetranatrolite chemical analyses shows that there is a continuous solid
solution series between gonnardite and tetranatrolite.
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Raade, G., Åmli, R., Mladeck,
M., Din, V. K., Larsen, A. O. & Åsheim, A. 1983: Chiavennite
from syenite pegmatites in the Oslo Region, Norway. American Mineralogist,
68, 628-633.
Chiavennite occurs as reddish
orange spherulites in vugs of syenite pegmatite at four different localities
in the southern Oslo Region of Norway. Chemical analysis and TGA give a
formula very close to CaMnBe2Si5O13(OH)2·2H2O.
The mineral is orthorhombic, a = 8.866(7), b = 31.34(2),
c
= 4.787(3) Å, Z = 4. The strongest reflections (d in Å,
(I/I1), (hkl)) of the powder pattern (diffractometer
data with preferred orientation) are: 15.7(55)(020), 7.84(25)(040), 5.84(15)(140),
3.917(100)(080), 3.260(15)(251), 3.889(15)(251). Chiavennite crystals have
the following properties: hemimorphic, spear-shaped, flattened on {010}
with pyramid {161}; good to perfect cleavages on {100}, {010}, and {001};
D(meas.) = 2.56 g/cm3, D(calc.) = 2.65 g/cm3 for
the ideal formula; optically biaxial positive, alpha = 1.596(2), beta =
1.600(2), gamma = 1.618(2) in white light; 2Vz (calc.)
50º; weak pleochroism in pale yeallowish brown, X < Z;
and optical orientation X = a, Y = b, Z
= c.
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Raade, G., Haug, J., Kristiansen,
R. & Larsen, A. O. 1980: Langesundsfjord. Lapis, 5, 22-28.
This paper gives a brief introduction
to the history and geology of the syenite pegmatites in the Oslo Region,
plus a complete list of minerals found in these pegmatites. A comparison
of the syenite pegmatites in the Oslo Region with other alkaline localities
worldwide is also given.
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Raade, G. & Larsen, A. O.
1980: Polylithionite from syenite pegmatite at Vøra, Sandefjord,
Oslo Region, Norway. Contribution to the mineralogy of Norway, No. 65.
Norsk
Geologisk Tidsskrift, 60, 117-124.
Polylithionite from Vøra
has a chemical composition close to the ideal end-member formula KLi2AlSi4O10F2.
It has the 1M polytype structure with a = 5.196(4), b = 8.980(4),
c
= 10.051(4) Å, beta = 100.29(5)º. The measured density is 2.82(1)
g/cm3, the calculated density 2.84 g/cm3. Optical
measurements gave beta = 1.556(1), gamma = 1.559(1), 2Va
= 43(3)º on one sample and beta = 1.555(1), gamme = 1.555(1) on another.
DTA/TGA curves and infrared spectrum are given. The mineral paragenesis
of the Vøra syenite pegmatite is reported, and data are given that
indicate enrichment of Li in the dark mineral constituents. The Gladstone-Dale
relationship applied to micas is shown to give better agreement between
calculated and measured mean refractive index using k-values from
Larsen & Berman (1934) than using the values of Mandarino (1976).
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Segalstad, T. V. & Larsen,
A. O. 1978: Gadolinite-(Ce) from Skien, southwestern Oslo Region, Norway.
American
Mineralogist, 63, 188-195.
Cerium-rich gadolinite containing
the larger REE occurs in a syenite pegmatite near Skien, Norway. It shows
REE zoning with a rim rich in Ce and poor in Y (25 weight percent Ce2O3;
2 weight percent Y2O3) relative to the core (15 weight
percent Ce2O3; 14 weight percent Y2O3).
X-ray studies show that the unit cell is slightly larger than for gadolinites-(Y).
The chondrite-normalized REE pattern of the gadolinite-(Ce) show strong
enrichment of the larger REE relative to the smaller REE. This is believed
to be related to the larvikite-derived pegmatite liquids; it is not believed
to have resulted through leaching of the basaltic country rock.
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Segalstad, T. V. & Larsen,
A. O. 1978: Chevkinite and perrierite from the Oslo Region, Norway. American
Mineralogist, 63, 499-505.
Chevkinite has been found in three
localities of syenite pegmatite in the Oslo region, one which also carries
perrierite. The perrierite and chevkinite do not coexist. The perrierite
contains a loparite (with pyrophanite) core. The unheated chevkinites and
perrierite gave no X-ray diffraction patterns, due to their metamict state.
All chevkinites show well developed chevkinite X-ray pattern when heated
in air, but in the sample with Ce>La the chevkinite pattern is weak and
strong CeO2 pattern is also present. Unit-cell dimensions correspond
with cell parameters given in the literature. The chemical compositions
of the chevkinites and perrierite investigated were found to be relatively
uniform and suited the formula A4BC4Si4O22
where A = REE, Th, Ca, Sr, Na, K; B = Fe2+, Mg,
Mn, Ca; C = Ti, Mg, Mn, Fe2+, Fe3+, Al. Phase
boundaries for the structural transformations between natural chevkinites
and perrierites are given as a function of the average size of the ions
occupying the several structural sites. The result of the study tend to
confirm that the phase change chevkinite-perrierite is controlled primarily
by composition, in that the size of the B and C cations exerts
a strong control over the structure. In the chevkinite structure very large
cations can therefore only be accomodated in the A positions either
by increasing the average size of the B and C cations to
open up the structure or by distorting it to give perrierite symmetry.
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