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Tweddillite from
Praborna Mine, Saint-Marcel, Aosta Valley, Italy

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Tweddillite, etc.

Praborna Mine, Saint-Marcel, Aosta Valley, Italy

Tweddillite, etc.

Praborna Mine, Saint-Marcel, Aosta Valley, Italy

Tweddillite, etc.

Praborna Mine, Saint-Marcel, Aosta Valley, Italy

Locality type:

Mine

Classification

Species:

Tweddillite

Formula:

(CaSr)(Mn³⁺AlMn³⁺)O[Si₂O₇][SiO₄](OH)

Chemical Analyses:

Oxide wt%:

	1	2
SiO₂	32.6 %	33.0 %
ThO₂	0.2 %	0.2 %
Al₂O₃	12.9 %	13.6 %
Ga₂O₃	0.1 %	%
Cr₂O₃	0.1 %	%
La₂O₃	9.2 %	3.1 %
Ce₂O₃	0.2 %	0.3 %
Pr₂O₃	1.5 %	0.8 %
Nd₂O₃	2.6 %	1.9 %
Sm₂O₃	0.1 %	0.1 %
Mn₂O₃	15.0 %	19.4 %
Fe₂O₃	1.5 %	1.2 %
MnO	1.4 %	0.9 %
MgO	2.2 %	0.6 %
CaO	10.6 %	13.7 %
SrO	7.2 %	8.6 %
Na₂O	0.5 %	0.2 %
H₂O	1.6 %	1.7 %
Total:	99.5 %	99.3 %

Sample references:

1	pt. 23	Frank K. Mazdab collection, thin section FKM-171 (https://www.rockptx.com/fkm-151-to-fkm-175/#FKM-171)
2	pt. 34	Frank K. Mazdab collection, thin section FKM-171 (https://www.rockptx.com/fkm-151-to-fkm-175/#FKM-171)

Comments:

For normalized analyses of tweddillite and piemontite from this locality, as well as data for accompanying minerals in the examined thin section, see:
https://www.rockptx.com/fkm-151-to-fkm-175/#FKM-171

In my instructional YouTube video tutorial on "Normalizing epidote-group minerals in MS Excel" (https://www.youtube.com/watch?v=IbMLngyz4Cs), the Prabornaz mine "piemontite" analysis I used to illustrate the normalization calculations turned out to be a REE-bearing tweddillite (named as "manganipiemontite-(Sr)" based on the Armbruster et al., 2006 nomenclature).

The sample for this thin section was collected by Pilar Lecumberri-Sanchez (Univ. Arizona) on a field trip to the locality.

Colour:

in thin section, pleochroic in yellow, orange, red and magenta; similar to and essentially indistinguishable from other Mn-rich members of the epidote group.

Confirmation

Validity:

Believed Valid

Associated Minerals Based on Photo Data:

Strontium-bearing Piemontite

ⓘ1 photo of Tweddillite associated with Strontium-bearing Piemontite at this locality.

Braunite

ⓘ1 photo of Tweddillite associated with Braunite at this locality.

Cryptomelane

ⓘ1 photo of Tweddillite associated with Cryptomelane at this locality.

Aegirine

ⓘ1 photo of Tweddillite associated with Aegirine at this locality.

Alurgite

ⓘ1 photo of Tweddillite associated with Alurgite at this locality.

Data

Mineral Data:

Click here to view Tweddillite data

Locality Data:

Click here to view Praborna Mine, Saint-Marcel, Aosta Valley, Italy

Data Identifiers

Mindat Occurrence Record ID:

1068325

Long-form Identifier:

1:3:1068325:5

GUID (UUID V4):

e5ca0ad9-fc76-4a94-89ae-de03cd37f850

References

Frank K. Mazdab collection (see https://www.rockptx.com/fkm-151-to-fkm-175/#FKM-171 for normalized analysis)

Reference Search (possible matching items)

	*Lauf, Robert J. (2011) Collector's Guide to the Epidote Group. Rocks & Minerals, 86 (5) 444-457 doi:10.1080/00357529.2011.602297*	Journal (article/letter/editorial)
	species were either very recently described (e.g., tweddillite) and/or uncommon to begin with (e.g., hancockite)...clinozoisite-(Sr); hancockite is now epidote-(Pb); tweddillite is now manganipiemontite-(Sr); strontiopiemontite...found at Hashupa and at Alchuri, in the Shigar Valley, Northern Areas, Pakistan (Blauwet 2006). • Good...striated epidotes in matrix, from the Calumet iron mine, Colorado. Epidote was described in 1801 by Haüy...collectors. Within the United States, the Green Monster mine, Prince of Wales Island, Alaska, has yielded superb
	Armbruster, Thomas, Bonazzi, Paola, Akasaka, Masahide, Bermanec, Vladimir, Chopin, Christian, Gieré, Reto, Heuss-Assbichler, Soraya, Liebscher, Axel, Menchetti, Silvio, Pan, Yuanming, Pasero, Marco (2006) Recommended nomenclature of epidote-group minerals. European Journal of Mineralogy, 18 (5) 551-567 doi:10.1127/0935-1221/2006/0018-0551	Journal (article/letter/editorial)
	dell’Università di Firenze, Via La Pira 4, I-50121 Firenze, Italy 3Department of Geoscience, Faculty of Science and...Università di Pisa, Via S. Maria 53, I-56126 Pisa, Italy Abstract: Epidote-group minerals are monoclinic...(new), hancockite (old) = epidote-(Pb) (new), tweddillite (old) = manganipiemontite-(Sr) (new). Minor modifications...identity with epidote. Withamite from the Yamanaka mine (Japan) described by Yoshimura & Momoi (1964) is...Fouquéite = Piemontite (Bourg Clinozoisite (St. Marcel) d’Oisans) (Sri Lanka) SiO2 36.49 38.6 38.64 22
	Pieczka, A., Kristiansen, R., Stachowicz, M., Dumańska-Słowik, M., Gołębiowska, B., Sęk, M., Woźniak, K. (2024) Heflikite, ideally Ca2(Al2Sc)(Si2O7)(SiO4)O(OH), the first scandium epidote-supergroup mineral from Jordanów Śląski, Lower Silesia (Poland) and from Heftetjern, Tørdal (Norway) Mineralogical Magazine. doi:10.1180/mgm.2023.98	Journal (article/letter/editorial)
	and Medenbach O. (2002) Manganvesuvianite and tweddillite, two new Mn3+-silicate minerals from the Kalahari...the epidote group, from Val Graveglia, Liguria, Italy. European Journal of Mineralogy, 2, 519–523. Catti...region of monoclinic epidotes from Praborna (St. Marcel, Aosta Valley, Italy). European Journal of Mineralogy...Ca2Al2Fe3+(Si2O7)(SiO4)O(OH), a new mineral from the Ananai mine, Kochi Prefecture, Japan. Journal of the Mineralogical...(2006) Allanite-(La) from Buca Della Vena Mine, Apuan Alps, Italy, an epidote-group mineral. The Canadian
	*Hyršl, Jaroslav, Bernard, Jan (2013) Minerals and their Localities* - Supplement - Minerals described since 2004. Granit, Prague.**	Book (edition)
	MINE andtheir LOCALITIES JAN H. BERNARD AND JAROSLAV HYRSL INERALS DESCRIBED SINCE 2004 MINERALS...dist., China Fluomatromicrolite, x 25111111, Naipa mine, Mozambique Daliranite, 5111111, Zarshouran Au-As...Domafov, Czech Rep. Juangodoyite, 60111111, Santa Rosa mine, Chile Back cover photo: Ho/fertile on hematite...piment pseudomo,phs after realga,; 75 mm, Palomo mine, Pen, Page 3: Stepite on arsenic, 45 111111,Jachymov...Saint Sainte island mount, mountain Mts. R. Penin. Vole
	*Liebscher, Axel, Franz, Gerhard - Eds.* (2004) Epidotes. Reviews in Mineralogy and Geochemistry Vol. 56. Mineralogical Society of America**	Report (volume)
	according to the type locality Piemont in Northern Italy. The first Cr rich epidote occurrence was described...in zoisite; sample HU93-8 from Sterzing, Tauern/Italy; photomicrograph with crossed polarized light (c)...REE-bearing piemontite from Monte Brugiana, Alpi Apuane, Italy. Eur J Mineral 4:23–34 Bonazzi P, Menchetti S (1995)...the epidote group, from Val Graveglia, Liguria, Italy. Eur J Mineral 2:519-523 Bonazzi P, Menchetti S...Cordier L (1803) Analyse du Minéralconnu sus le nom de Mine de Manganese violet du Piédmont, faite au Labratoire
	*Bernard, Jan, Hyršl, Jaroslav (2004) Minerals and their Localities* (1st ed.) Granit, Prague.**	Book (edition)
	Linopolis, Brazil, H Page 13: Gold, 35 mm.Eagle's est Mine, California, G Publi!>hed by Grdllit.u.o. Stefanikova43...(island), Vole. (volcano), Penin. (peninsula), St. (Saint), Ste. (Sainte). Recent developments in many countries...Rice, Dolores co., both Colorado, at the Questa mine, Taos co., New 1994. Abernathyite K2[(UOJ 2l(AsO_J2]•6HzO...Harding Co .. South Dakota. and at the Fuemrole No2 mine, Emery co .. Utah. Also at Menzenschwand Scbwarzwald...mainly in crystals to 5 cm at the Himmelsftirst mine, Freiberg, both Saxony, Germany. In the subtropical

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Tweddillite from Praborna Mine, Saint-Marcel, Aosta Valley, Italy

Tweddillite from
Praborna Mine, Saint-Marcel, Aosta Valley, Italy