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REPORT ON THE MINERALOGY OF A SAMPLE FROM THE
AGRICOLA RESOURCES ENERGY RIDGE PROSPECT
HAUTAJAERVI, LAPIN LAANI, FINLAND
Christopher Halls PhD
Associate
Department of Mineralogy
NHM
London
21 November 2005
1
Contents
Figures
Figure 1
Geological map of the Kuusamo Schist Belt Finland, showing the location of the Hautajaervi
claims with the Energy Ridge prospect.
Figure 2
Photograph of exposure in Trench A, Agricola Resources Energy Ridge prospect, Hautajaervi
claims.
Macrophotograph of the polished block containing the Energy Ridge sample.
Figure 3
Figure 4
Backscattered electron micrograph of amphibole matrix with secondary uranium minerals filling
fractures. Semi-quantitative analysis of elements present in edenite.
Figure 5
23-1045)
Diffraction peaks of the Energy Ridge amphibole compared to reference edenite (PDF number
Figure 6
Backscattered electron micrograph showing aggregate of oxidised pyrite and secondary
uranium minerals with stacked X-ray spectra.
Figure 7
Backscattered electron micrograph showing widenmannite forming filling of fracture in edenite.
Figure 8
Backscattered electron micrograph showing widenmannite core in altered aggregate together
with characteristic X-ray spectrum.
Figure 9
Backscattered electron micrograph of detail in pure widenmannite aggregate to show tabular
morphology of crystallites.
Figure 9a
Semi-quantitative analysis of pure widenmannite aggregate.
Figure 10
Backscattered electron micrograph showing detail of oxidised aggregate with widenmannite
and altered pyrite. X-ray spectra in stacked format.
Figure 11
Backscattered electron micrograph showing calcite with uranophane located in cleavage.
Figure 11a
Detail showing uranophane from cleavage with semi-quantitative analysis.
Figure 12
Backscattered electron micrograph showing magnetite grain in edenite.
Figure 13
Nucleus of secondary widenmannite in oxidised aggregate of pyrite.
Figure 14
Backscattered electron micrograph showing detail of mosaic pattern in altered pyrite with
associated widenmannite.
Figure 15
Diagram from Garrels and Christ (1965) showing the wide field of stability of uranyl carbonate
ionic species under ambient conditions in the natural environment.
Table 1
List of lattice planes and parameters for reference edenite (PDF number 23 1045).
Acknowledgements
The analyses presented in this report were made using the JEOL scanning electron microscope and the
Nonius X-ray diffractometer in the Department of Mineralogy at the Natural History Museum by courtesy of
Dr Andy Fleet, Keeper of Mineralogy. Expert assistance in the gathering of images and analyses was provided
by Mr Anton Kearsley Mr John Spratt, and Ms Caroline Kirk
2
Introduction
A small sample of rock taken from outcrop in Trench A of the Agricola Resources Energy Ridge prospect on
the Hautajaervi claims in the Kuusamo Schist Belt of Lapin Laani County in Finland was submitted for
mineralogical analysis. The setting in relationship to the geology of the Kuusamo Schist Belt is shown in the
map Figure 1. The outcrop of this rock exposed by trenching is shown in the photograph, Figure 2, taken
from the Agricola Resources plc website http://www.agricolaresources.com.
Based on the results of scintillometry and multielement chemical analysis carried out in the laboratories of
the Geological Survey of Finland, the rock is known to contain greater than 0.36 wt % of U3O8 , together with
significant amounts of Na2O, K2O, MgO, Fe2O3 , CaO, Al2O3 (reaching 50 wt %) TiO2,and SiO2. P2O5 and Pb
are also present in minor amounts. The sample was taken from a ten metre interval over which the average
grade of uranium is 0.36 wt% U3O8 , and the CaO content reaches values as high as 50 wt%.
Mineralogical investigation of the sample has been carried out with the aim of identifying the main mineral
components of the rock and, in particular, to determine the uranium-bearing phases that are present.
Preparation of sample material and analytical methods
Using a Geiger counter, the sample was tested for radioactivity. The count rate was significantly above
background confirming the presence of radioactive elements in the rock. The sample was cut using a
diamond saw and two fragments were mounted in a resin block and polished so that semi-quantitative
energy dispersive X-ray analysis of the minerals could be made using the JEOL JSM 5900 LV scanning
electron microscope in the Department of Mineralogy at the NHM. A small fragment of the dark green
ferromagnesian mineral from the sample was crushed to a powder in an agate pestle and mortar so that a
definite identification could be made using the Nonius CPS 120 powder diffractometer in the Department of
Mineralogy at the NHM. This enabled a specific identification of the amphibole mineral for which only an
approximate chemical analysis could be obtained using the JSM 5900 in semi-quantitative analytical mode.
Description of the Energy Ridge sample
A macrophotograph of the two fragments of the rock, mounted and polished in a resin block, is shown in
Figure 3. There are two distinct areas in the rock that contrast markedly in colour. One is the blackish green
aggregate of subhedral ferromagnesian minerals. The other forms the matrix of pink and colourless minerals
in which the dark green material is set. The external characteristics of this sample therefore match those of
the outcrop from which it was collected (see Figure 2). A tentative identification of the dark green mineral as
tourmaline is made in the caption on the Agricola Resources plc website. The well-developed prismatic
cleavage of the mineral suggests that it is more likely a pyroxene or amphibole. The basal/oblique sections
visible on the polished surface of the sample show partly rhombic outlines with an obtuse angle between
faces of about 124o. Based on this characteristic, the mineral preliminarily identified as an amphibole. The
cleavage surfaces exposed by splitting the grains with a steel engraving tool are lustrous and bright showing
that the mineral has not been significantly altered to chlorite. Examination of the specimen using a hand lens
shows that some biotite is also present. The pink matrix in which the ferromagnesian minerals are set is
relatively soft (Mohs hardness 3) and has a good rhombohedral cleavage. It is therefore likely to be a
carbonate.
In addition to the major minerals making up the rock, small grains of an iron grey magnetic phase are
present. These can be seen with a hand lens and a pen magnet is attracted to the corresponding points on
the polished surface. This confirms that accessory magnetite is present in the rock.
Small yellowish flecks are present on the macrophotograph of the polished surface (Figure 3). These are the
secondary uranium minerals which are described as coating the surface of the outcrop in Trench A shown
in Figure 2. Their presence on the polished surface suggests that uranium bearing mineral aggregates occur
not only as surface coatings but also distributed within the mass of the rock.
3
Results of analysis of the Energy Ridge sample
The polished block was coated with carbon and placed in the specimen chamber of the JEOL JSM 5900 LV
scanning electron microscope. A reconnaissance of the polished surface was made using the instrument in
the scanning mode. Backscattered electron images of the scanned surface enable a distinction to be made
between mineral phases consisting of elements with high atomic numbers and those with elements having
lower atomic numbers. Backscattering of electrons from the electron beam is greater when the nuclei of the
constituent elements are heavier. Thus the minerals containing heavier elements show up brightly, whereas
the less heavy phases appear darker in the grey scale of the image. For this reason, minerals in which
uranium is a constituent element show up brightly against areas of the common rock forming silicates and
gangue. Uranium has an atomic number of 92 and is the heaviest of the common elements in the periodic
table.
Using the contrast in the backscattered electron images, the areas of uranium-bearing phases were quickly
identified and a selection of images were captured. The images were then used to control the selection of
points for semi-quantitative analysis of the uranium minerals and the minerals in the surrounding matrix.
When operated in analytical mode, the JEOL JSM 5900 LV combined with Oxford Instruments Inca software
can graphically display the energy dispersive spectra of the characteristic X-ray peaks emitted by the
constituent elements in the mineral as they are bombarded by the focussed electron micro beam.
Based on the counts obtained for characteristic X-rays emitted within defined energy ranges, a semiquantitative analysis of the mineral can be rapidly calculated using the Inca programme. In the case of binary
and ternary compounds, these semi-quantitative analyses usually allow an unambiguous identification of the
mineral to be made. If the mineral belongs to a complex silicate mineral group like the pyroxenes or
amphiboles, the semi-quantitative analysis will often only allow a rough identification of the phase concerned.
In such a case, further confirmation can be obtained by using X-ray diffractometry to provide information
about the lattice structure of the mineral concerned. To obtain an unequivocal identity for the amphibole in
the Energy Ridge sample, this option was chosen. The Nonius CPS 120 diffractometer with an Inel position
sensitive detector was used to collect a spectrum of the X-ray diffraction peaks from a powdered sample of
the dark green mineral.
The results of the semi-quantitative analysis of elements contained in the amphibole, combined with the
match between the diffractometry peaks for the various planes in the lattice structure show that the
amphibole is edenite NaCa2(MgFe)5(AlSi7)O22(OH)2
A semi-quantitative analysis of edenite with the corresponding backscattered electron micrograph captured
using the JEOL JSM 5900 LV is shown in Figure 4. The micrograph also shows the bright secondary uranium
minerals-filling fractures in the edenite matrix. Figure 5 shows the diffraction peaks of the amphibole from
Trench A, Energy Ridge, matched against the diagnostic peaks for edenite stored in the XRD powder
diffraction reference archive. The comparison has been made with reference sample PDF number 23-1045.
The full details of the reflections characteristic of the reference edenite sample are given in Table 1.
Reconnaissance of the polished sample using backscattered electron imagery allowed the uraniferous phases
in the rock to be rapidly located.
The uraniferous minerals occur in two different situations in the rock:
1) The larger areas of uranium minerals coincide with the pale yellow spots (0.5-1.5mm diameter) which
are clearly visible in the macrophotograph, Figure 3. The areas are aggregates in which a central core
of secondary uranium minerals is partly surrounded by and intergrown with pyrite which itself is partly
oxidised to secondary sulphates. The characteristic mineralogies of these aggregates are shown in
Figures 6, 8, 10, 13 and 14
2) Within the host amphibole and the pink carbonate matrix, thin veinlets (10-40 microns wide) of
secondary uranium minerals fill cleavages and fractures. In many cases, these veinlets are distributed
around the larger aggregates. Typical examples are shown in Figures 4, 7 and 11. Characteristic X-ray
spectra from these thin veins frequently include peaks of elements present in the surrounding matrix.
In other cases, the spectrum and semi-quantitative analysis is good enough to allow identification.
4
A typical aggregate of the first type containing a core of secondary uranium minerals and surrounded by
partly oxidised pyrite is shown in the backscatter electron micrograph Figure 6. The X-ray spectra from
several points in the aggregate and surrounding matrix are given in a stacked format below the micrograph.
The secondary uranium mineral in the core of the aggregate displays characteristic peaks for the elements U,
Pb, and C. It should be noted that the specimen has been coated with carbon to ensure a conducting surface
so that charge from the electron beam does not build up on the specimen surface. For this reason a carbon
peak will be detected whether the mineral contains carbon in its structure or not. In this case, the carbon
peak is much higher than that produced by X-ray emission from the coating alone, and therefore carbon must
be present in the mineral structure.
Based on semi-quantitative analysis of several aggregates and homogeneous areas of this mineral (Figures 6,
7, 8, 9a, 10, and 13), the secondary uranium mineral is identified as widenmannite. This is a lead uranyl
carbonate having the formula Pb2(UO2)(CO3)3.
Widenmannite is a soft (Mohs hardness 2), pale yellow mineral with a nacreous lustre, perfect cleavage
[100], a tabular habit and a density of 6.89. Because of the uranium it contains, it is radioactive, producing
greater than 70 Bq/gramme. The macrophotograph provides confirmation of the colour of the mineral and
the electron micrographs show the densely packed tabular crystallites which form the cores of the larger
aggregates (Figure 9) and the segregated veinlets (Figure 7). The mineral was first described in 1961 by
Walenta and Wimmenauer from the Michael Vein in Weiler bei Lehr, Schwarzwald, Germany and was named
for Bergrat J.F. Widenmann (1764-1798) who first discovered ‘uranium micas’ in the Schwarzwald. In the
Michael vein, the widenmannite occurs in association with galena and cerussite.
In addition to the widenmannite that forms the cores of all the uraniferous aggregates in the specimen from
Energy Ridge, and fills many of the veinlets in the surrounding minerals, some other secondary uranium
minerals are also present in fine veinlets. The spectra obtained from these indicate the presence of
uranophane and probably also some autunite (Figure 11a).
The matrix of the widenmannite in the aggregates shows characteristic X-ray peaks indicating the presence
of thorium, LREE and phosphorus, as well as U and lead (Figure 10). This association of elements is not
readily ascribed to a single mineral and the matrix is, in all probability a mixture of at least two secondary
phases.
Conclusions
Semi-quantitative energy-dispersive analysis of the X-ray spectra generated by the electron beam on
selected points in the minerals composing the rock sample from the Agricola Resources Energy Ridge
prospect indicate that the main minerals present are amphibole (edenite), biotite, albite and calcite.
Accessory Fe-Ti oxide phases are magnetite and ilmenite. The uranium minerals present are the secondary
uranyl lead carbonate widenmannite, together with minor amounts of the calcium uranyl silicate uranophane.
Much of the widenmannite is found in mm scale aggregates together with pyrite that is partly altered to
secondary sulphate minerals such as jarosite.
The atomic ratio Pb:U indicated by the stoichiometry of the widenmannite formula is 2:1 so this secondary
mineral is relatively lead rich. No remains of a lead-rich precursor mineral have been detected, so the original
mineralogical source of the lead in the widenmannite is open to speculation. Some of the lead may have been
generated as a result of the breakdown of the radioactive isotopes of U. The most likely candidate mineral to
provide a source of lead would be galena PbS, as is the case at the type locality, the Michael Vein in the
Schwarzwald. Uranium could originally have been present as uraninite UO2 .The euhedral shapes visible
around the widenmannite cores suggest that the original aggregates may have been a mixture of euhedral
pyrite and uraninite. This hypothesis fails to account for the presence of Th, LREE and P in the matrix
surrounding the cores of pure widenmannite.
The presence of secondary uranyl compounds in the Energy Ridge sample is a natural consequence of
oxidation of precursor minerals carrying uranium in the U4+ state. The wide range of conditions under which
complex uranyl carbonate ions are stable at near ambient temperatures in the natural environment is shown
in the Eh-pH-PCO2 diagram (Figure) taken from Garrels and Christ (1965). At Energy Ridge the uranyl
carbonate ions have combined mainly with Pb and Ca.
5
The association of rock-forming minerals in the Energy Ridge sample shows that the rock has affinities with
alkaline carbonic eruptives. This conclusion is supported by the presence of LREE and phosphorus, as well as
uranium in the accessory paragenesis. Edenite was first described from the Franklin Marble, a formation that
extends from the famous mines of Franklin, New Jersey, to New York. In fact, the fine specimen of edenite on
display at the Smithsonian Museum is from Finland!
The Agricola Hautajaervi claims are located in the meta-eruptive unit of the Palaeoproterozoic Kuusamo
Schist Belt which has been interpreted as a failed intracontinental rift within an Archaean platform. The
metallogeny of the belt is characterised by the distinctive association of
the elements Cu-Co-U-LREE (Au). Intense albitisation is also a feature of the deuteric/metamorphic history of
the eruptives in this belt. This geochemical pattern has been well-described in the literature and is
summarised in the Geological Survey of Finland site (www.gtk.fi/explor/gold_review.htm) where additional
references can be found.
The mineralogy and geochemistry of the Energy Ridge rock sample fits well within the context of the
Kuusamo Schist belt, but further mineralogical study of fresh rocks will be necessary to determine the
identity of the primary uranium bearing minerals from which the secondary paragenesis at Energy Ridge has
been formed.
References
Garrels R.M. and Christ C.L. (1965)
Solutions, Minerals and Equilibria. Harper and Row, New York, 450p
Hey M.H. (1961)
Twenty-second list of new mineral names. Mineralogical Magazine, 32,
p.941-961.
Walenta K. and Wimmenauer W (1961)
Jahresheft geol. Landesamt Baden-Wurttemburg, 4, p.22
6
FIGURE 1 Geological map showing the position of the Agricola Energy Ridge prospect in the Hautajaervi
sector of the Kuusamo Schist Belt
7
FIGURE 2 - Exposure of uraniferous rock in Trench A from which the sample was obtained. The dark green
mineral is the amphibole edenite. The pink mineral is calcite with some albite intergrown. Yellowish
secondary uranium minerals coat the upper surface.
8
FIGURE 3 - Macrophotograph of sample of uraniferous rock from Trench A, Energy Ridge, Agricola
Hautajarvi prospect, Kuusamo Schist Belt, Lapin Laani, Finland. Polished block with two fragments mounted
in resin.
The dark mineral forming most of the rock is the amphibole edenite NaCa2(MgFe)5(AlSi7)O22(OH)2, also
intergrown with some biotite, and containing accessory grains of magnetite and ilmenite. The pink mineral
forming a partial matrix for the pyroxene is calcite, showing rhombohedral cleavage. The clear (grey) silicate
grains included within the calcite in the smaller fragment to the right are albite.
The yellow flecks in the pyroxene and calcite of the larger fragment are aggregates of secondary uranium
minerals associated with oxidised pyrite. The main secondary uranium minerals are widenmannite
Pb2(UO2)(CO3)3, a lead uranyl carbonate, and uranophane Ca(UO2)2[SiO3(OH)]2.5H2O, a hydrated calcium
uranyl silicate. Identity of minerals determined by semi-quantitative energy dispersive x-ray analysis using
the JEOL JSM-5900 LV scanning electron microscope in the Department of Mineralogy at the Natural History
Museum, London.
Scale: Diameter of polished block is 4cm¨
9
FIGURE 4 - Electron backscatter micrograph showing the amphibole edenite forming a matrix for secondary
uranyl minerals (bright grey) filling fractures. The identity of edenite was confirmed by X-ray diffractometry
using a Nonius CPS 120 powder diffractometer with an INEL position sensitive detector. Diffraction peaks with
match against reference edenite shown in Figure 5
No peaks omitted
Processing option : Oxygen by stoichiometry (Normalised)
Number of iterations = 3
Eleme
nt
Weight
%
Atomic
%
Compd
%
Formul
a
Na K
Mg K
Al K
Si K
Ca K
Fe K
O
0.58
11.07
1.15
26.11
8.33
8.70
44.07
0.55
9.96
0.93
20.34
4.55
3.41
60.27
0.78
18.35
2.17
55.86
11.66
11.19
Na2O
MgO
Al2O3
SiO2
CaO
FeO
Totals
100.00
10
STOE Powder Diffraction Analysis
Nonius CPS120 Powder Diffractometer with Inel PSD
21-Nov-05
Finland Agricola Resources, Energy Ridge Prospect
[23-1405] Na Ca2 Mg5 Al Si7 O22 ( O H )2 / Sodium Calcium Magnesium Aluminum Silicate Hydroxide / Edenite
1000
Absolute Intensity
800
600
400
200
0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
2Theta
FIGURE 5 - Diffraction pattern of the amphibole mineral from Agricola Energy Ridge prospect. The best
match in the powder diffraction data base is with Edenite, (PDF number 23-1045). There are peaks observed
that are not part of the standard pattern, but this is probably due to the quality of the pattern. The
monoclinic unit cell of Edenite has calculated peaks coinciding with all those displayed in the pattern of the
Energy Ridge sample. This confirms edenite.
11
TABLE 1
Reference Pattern [23-1405] PDF-2 Sets 1-89
Quality: I
Wavelength: 1.540598
________________________________________________________________________________
Sodium Calcium Magnesium Aluminium Silicate Hydroxide
Na Ca2 Mg5 Al Si7 O22 ( O H )2
Edenite
________________________________________________________________________________
Rad.: CuKa (1.54178)
Filter: Beta Ni
d-sp:
I/Icor.:
Cutoff:
Int.: Diffractometer
Ref.: Department of Geology, University of Durham, Durham, England, UK., ICDD
Grant-in-Aid
________________________________________________________________________________
System: Monoclinic
Spacegroup: C2/m (12)
a: 9.837
b: 17.954
c: 5.307
a/b: 0.5479 c/b: 0.2956
A:
B: 105.18
C:
V: 904.6
Z: 2
Dx: 3.062
Dm:
Mp:
SS/FOM: F23 = 7.8 ( 0.0350, 83 ) FOM(DeWolff): 8.4
________________________________________________________________________________
Color: Green, black
________________________________________________________________________________
Optical data on specimen from Eganville, Ontario, Canada. Specimen from
Franklin Furnace, New Jersey, USA. See ICSD 79138 (PDF 01-083-0056).
________________________________________________________________________________
d[Å] 2Theta Int.
h k l
d[Å] 2Theta Int.
h k l
________________________________________________________________________________
9.0100
8.4300
4.9100
4.5000
3.8870
9.809 10
10.486 80
18.052 4
19.713 10
22.860 4
0
1
-1
0
-1
2
1
1
4
3
0
0
1
0
1
2.3380 38.473 10
2.2930 39.259 4
2.2210 40.587 2
2.1550 41.887 8
2.0430 44.301 4
3.3770
3.2670
3.1200
2.9330
2.8000
26.371 12
27.275 40
28.587 100
30.453 12
31.937 18
0
2
3
2
3
4
4
1
2
3
1
0
0
1
0
2.0100 45.068 10
1.9570 46.359 2
1.8590 48.958 2
2.7370
2.6990
2.5870
2.5490
2.3760
32.692
33.166
34.646
35.179
37.834
-3
1
0
-2
3
3
5
6
0
5
1
1
1
2
0
10
20
8
10
10
-3
-1
0
-3
2
5
7
4
3
0
1
1
2
2
2
3 5 1
1 9 0
4 6 0
________________________________________________________________________________
12
FIGURE 6 - Backscattered electron micrograph showing aggregate of oxidised pyrite and secondary uranium
minerals in biotite matrix. Characteristic X-ray spectra are (1)-biotite; (2)-pyrite; (3)-widenmannite (lead
uranyl carbonate); (4) jarosite
13
FIGURE 7. Widenmannite (lead uranyl carbonate) Pb2 (UO2) (CO3)3 filling fracture in edenite. Note
prominence of carbon peak (C).
14
FIGURE 8. Electron backscatter micrograph of widenmannite core in secondary aggregate showing
characteristic X-ray spectrum. Iron peaks are from products of pyrite oxidation.
15
FIGURE 9 - Backscattered electron micrograph showing tabular morphology in area of secondary lead uranyl
carbonate, widenmannite, in silicate matrix. Diagnostic X-ray spectrum.
16
FIGURE 9a: - Semi-quantitative analysis of pure widenmannite aggregate. Note the stoichiometric
proportions of Pb and Uranium which are present in the ratio Pb:U approximately 2:1.
No peaks omitted
Semi-quantitative analysis
Processing option : Oxygen by stoichiometry (Normalised)
Number of iterations = 3
Eleme
nt
Weight
%
Atomic
%
Compd
%
Formul
a
Pb M
UM
O
Totals
51.86
36.73
11.41
100.00
22.39
13.80
63.80
55.87
44.13
PbO
UO3
Figure: Backscattered electron micrograph showing area of nearly pure lead uranyl carbonate, widenmannite,
and analysis of constituent elements, omitting carbon.
17
FIGURE 10 - Backscattered electron micrograph showing aggregate of secondary uranium minerals and
oxidised pyrite with stacked X-ray spectra corresponding to specific phases and mixtures in the aggregate.
Spectra 1, 2 and 5 show elements characteristic of Widenmannite with addition of thorium. Spectra 3 and 4
indicate pyrite and secondary sulphate
18
FIGURE 11. Backscattered electron micrograph showing calcite (spectrum 1) and amphibole (spectrum 2)
with secondary uranyl compound filling fractures in calcite. Note that an analysis of the carbon in the
carbonate is not computed because carbon is used as a conductive coating on the specimen. However, a
proportionally high carbon peak appears in the X-ray spectrum.
Note rhombohedral cleavage traces in calcite. This is the pink matrix seen in Figure 2.
Processing option : Oxygen by stoichiometry (Normalised)
Spectru
m
In
stats.
Spectru
m1
Spectru
m2
Yes
Max.
Min.
Yes
Na
Mg
Si
6.6
2
6.5
4
56.8
5
6.6
2
0.0
0
6.5
4
0.0
0
56.8
5
0.00
Ca
100.0
0
0.56
100.0
0
0.56
Fe
Total
29.4
2
100.0
0
100.0
0
29.4
2
0.00
All results in compound%
19
FIGURE 11a - Backscattered electron micrograph showing veinlet filled by secondary uranophane, hydrated
calcium uranyl silicate Ca(UO2)2[SiO3(OH)]2.5H2O. A small amount of phosphorus is also detected so some
calcium uranyl phosphate is also likely to be present
No peaks omitted
Processing option : Oxygen by stoichiometry (Normalised)
Number of iterations = 3
Eleme
nt
Weight
%
Atomic
%
Compd
%
Formul
a
Si K
PK
Ca K
UM
O
Totals
6.45
0.28
5.63
64.66
22.99
100.00
11.00
0.43
6.73
13.01
68.83
13.79
0.63
7.88
77.70
SiO2
P2O5
CaO
UO3
Figure Backscattered electron micrograph showing fractures in calcite filled by secondary uranophane,
calcium uranyl silicate Ca (UO2)2 [SiO3(OH)]2.5H2O
20
FIGURE 12 Accessory magnetite included in edenite matrix
21
Spectrum processing :
No peaks omitted
Processing option : Oxygen by stoichiometry (Normalised)
Number of iterations = 3
Standard :
Fe Eagle Station 2okV 2nAFC 051018
Pb PbF2 1-Jun-1999 12:00 AM
U U 1-Jun-1999 12:00 AM
18-Oct-2005 03:56 PM
Eleme
nt
Weight
%
Atomic
%
Compd
%
Formul
a
Fe K
Pb M
UM
O
Totals
0.66
51.74
36.13
11.47
100.00
1.04
22.09
13.43
63.43
0.85
55.73
43.42
FeO
PbO
UO3
FIGURE Aggregate showing secondary lead uranyl carbonate, widenmannite, replacing unknown precursor
mineral
22
Spectrum processing :
No peaks omitted
Processing option : All elements analyzed (Normalised)
Number of iterations = 2
Standard :
S FeS b6 2nAFC 20kV 040901 2-Sep-2004 04:11 PM
Fe Eagle Station 2okV 2nAFC 051018 18-Oct-2005 03:56 PM
Eleme
nt
Weight
%
Atomic
%
SK
Fe K
52.57
47.43
65.88
34.12
Totals
100.00
FIGURE 14 - Partly altered pyrite with associated widenmannite (white). Detail from larger aggregate.
23
Figure 15 - Diagram taken from Garrels and Christ (1965) showing the wide field of stability of uranyl
carbonate ionic species under ambient conditions in the natural environment. See Garrels R.M. and Christ
C.L. (1965) Solutions, Minerals and Equilibria. Harper and Row, New York, 450p.
24