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Piergorite-(Ce)
A valid IMA mineral species
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About Piergorite-(Ce)
Formula:
Ca8(Ce,Th,La,Nd)2(Al0.5Fe3+0.5)(◻,Li,Be)2Si6B8O36(OH,F)2
Colour:
Colorless to pale yellow
Lustre:
Vitreous
Specific Gravity:
3.67 (Calculated)
Crystal System:
Monoclinic
Name:
After Giancarlo Pierini (b. 1929 Monsummano Terme, Tuscany, Italy) and Pietro Francesco Gorni (b. 1939, Varese, Lombardy, Italy), two well-known and keen Italian mineral collectors, members of AMI (Italian Micromineralogical Association). The name is a portmanteau after their surnames, PIERini and GORini.
Type Locality:
Unique Identifiers
Mindat ID:
27426
Long-form identifier:
mindat:1:1:27426:7
IMA Classification of Piergorite-(Ce)
Approved
IMA Formula:
Ca8Ce3+2AlLiSi6B8O36(OH)2
Approval year:
2005
First published:
2006
Classification of Piergorite-(Ce)
9.DL.10
9 : SILICATES (Germanates)
D : Inosilicates
L : Inosilicates with 5-periodic double chains, Si10O28
9 : SILICATES (Germanates)
D : Inosilicates
L : Inosilicates with 5-periodic double chains, Si10O28
54.2.0.0
54 : NESOSILICATES Borosilicates and Some Beryllosilicates
2 : Borosilicates and Some Beryllosilicates with B in [4] coordination
54 : NESOSILICATES Borosilicates and Some Beryllosilicates
2 : Borosilicates and Some Beryllosilicates with B in [4] coordination
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Pgo-Ce | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Piergorite-(Ce)
Vitreous
Transparency:
Translucent
Colour:
Colorless to pale yellow
Streak:
White
Tenacity:
Brittle
Cleavage:
Perfect
{010}
{010}
Density:
3.67 g/cm3 (Calculated)
Optical Data of Piergorite-(Ce)
Type:
Biaxial (-)
RI values:
nα = 1.717(1) nβ = 1.728(1) nγ = 1.735(1)
2V:
Measured: 68° (2), Calculated: 77°
Max. Birefringence:
δ = 0.018
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
None
Optical Extinction:
X = b; Z ∧ c = 7(1)°.
Pleochroism:
Non-pleochroic
Chemistry of Piergorite-(Ce)
Mindat Formula:
Ca8(Ce,Th,La,Nd)2(Al0.5Fe3+0.5)(◻,Li,Be)2Si6B8O36(OH,F)2
Element Weights:
Crystallography of Piergorite-(Ce)
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P2/b
Setting:
P2/a
Cell Parameters:
a = 28.097(3) Å, b = 4.777(1) Å, c = 10.236(2) Å
β = 96.81(1)°
β = 96.81(1)°
Ratio:
a:b:c = 5.882 : 1 : 2.143
Unit Cell V:
1,364.18 ų (Calculated from Unit Cell)
Z:
2
Twinning:
polysynthetic twinning on {100}; frequently, they show L-shaped form by further twinning on the {301}
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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View
CIF File Best | x | y | z | a | b | c
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Rotation
Stop | Start
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Labels
Console Off | On | Grey | Yellow
Console Off | On | Grey | Yellow
Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0004179 | Piergorite-(Ce) | Boiocchi M, Callegari A, Ottolini L (2006) The crystal structure of piergorite-(Ce), Ca8Ce2(Al0.5Fe3+0.5)Sum1(X,Li,Be)2Si6B8O36(OH,F)2: A new borosilicate from Vetralla, Italy, with a modified hellandite-type chain American Mineralogist 91 1170-1177 |  | 2006 | Vetralla, Italy | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.65 Å | (100.0) |
| 1.91 Å | (48.3) |
| 2.90 Å | (44.9) |
Comments:
Vetrella, Italy. Data from type description.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 3a: Earth’s earliest Hadean crust | >4.50 |
| 9 : Lava/xenolith minerals (hornfels, sanidinite facies) | |
| 10 : Basalt-hosted zeolite minerals | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Type Occurrence of Piergorite-(Ce)
Place of Conservation of Type Material:
Museo di Mineralogia, Dipartimento di Scienzedella Terra, Universita degli Studi di Pavia, Italy with catalog number 2005-001 OL.
Geological Setting of Type Material:
extremely thin, platy micro crystals and aggregates perched within small seams in a volcanic ejecta.
Associated Minerals at Type Locality:
Synonyms of Piergorite-(Ce)
Other Language Names for Piergorite-(Ce)
Dutch:Piergoriet-(Ce)
German:Piergorit-(Ce)
Tre Croci, Vetralla, Viterbo Province, Lazio, Italy