For Dr. Friedrich Wilhelm Conrad Eduard Bornhardt (20 April 1864 Braunschweig - 2 December 1946 Goslar), German geologist, engineer and explorer, and was Director of the Berlin College of Mines (Bergakademie) from 1907 to 1916.

Type Locality:

ⓘ Trogtal Quarries, Harz (Landkreis Goslar), Goslar District, Lower Saxony, Germany

Se analogue of Linnaeite.
Current status "grandfathered" but considered questionable by Bosi et al. (2019).
A mineral that appears to never have been analyzed; compare tyrrellite.

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Unique IdentifiersHide

Mindat ID:

726

Long-form identifier:

mindat:1:1:726:7

GUID
(UUID V4):

77d92722-49dd-44a1-b8ac-7af777532da9

Classification of BornhardtiteHide

IMA status:

Approved, 'Grandfathered' (first described prior to 1959)

First published:

1955

Type description reference:

Ramdohr, P., Schmitt, M. (1955) Vier neue natürliche Kobaltselenide vom Steinbruch Trogtal bei Laufenthal im Harz. Neues Jahrbuch für Mineralogie, Monatshefte: 1955: 133-142.

Strunz-mindat (2023):

2.DA.05

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
D : Metal Sulfides, M: S = 3 :4 and 2:3
A : M:S = 3:4

Dana 8th ed.:

2.10.1.5

2 : SULFIDES
10 : A_mB_nX_p, with (m+n):p = 3:4

Hey's CIM Ref.:

3.10.5

3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
10 : Sulphides etc. of Co

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

Symbol	Source	Reference
Bhd	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 BornhardtiteHide

Transparency:

Opaque

Colour:

Rose-red

Hardness:

4 on Mohs scale

Density:

6.166 g/cm³ (Calculated)

Optical Data of BornhardtiteHide

Reflectivity:

Wavelength	R
400nm	41.3%
420nm	42.8%
440nm	44.3%
460nm	45.4%
480nm	46.4%
500nm	47.2%
520nm	47.8%
540nm	48.4%
560nm	49.2%
580nm	49.2%
600nm	49.7%
620nm	50.2%
640nm	50.8%
660nm	51.4%
680nm	52.0%
700nm	52.7%

Graph shows reflectance levels at different wavelengths (in nm). Top of box is 100%. Peak reflectance is 52.7%.

Chemical Properties of BornhardtiteHide

Formula:

Co²⁺Co³⁺₂Se₄

Elements listed:

Co, Se - search for minerals with similar chemistry

Crystallography of BornhardtiteHide

Crystal System:

Isometric

Class (H-M):

m3m (4/m 3 2/m) - Hexoctahedral

Space Group:

Fd3m

Setting:

Fd3m

Cell Parameters:

a = 10.2(2) Å

Unit Cell V:

1,061.21 Å³ (Calculated from Unit Cell)

Morphology:

Massive

X-Ray Powder DiffractionHide

Powder Diffraction Data:

d-spacing	Intensity
2.7 Å	(100)
2.4 Å	(100)
2.3 Å	(100)
2.2 Å	(100)
2.0 Å	(100)
1.96 Å	(100)
1.42 Å	(100)

Comments:

Trogtal quarry, Germany.

Geological EnvironmentHide

Paragenetic Mode(s):

Paragenetic Mode	Earliest Age (Ga)
High-𝑇 alteration and/or metamorphism
33 : Minerals deposited by hydrothermal metal-rich fluids (see also [#12])

Geological Setting:

Hydrothermal

Type Occurrence of BornhardtiteHide

Type Locality:

ⓘ Trogtal Quarries, Harz (Landkreis Goslar), Goslar District, Lower Saxony, Germany

General Appearance of Type Material:

Fine violet to red-brown intergrowths in clausthalite.

Place of Conservation of Type Material:

n.d.

Associated Minerals at Type Locality:

Reference:

Ramdohr, P., Schmitt, M. (1955) Vier neue natürliche Kobaltselenide vom Steinbruch Trogtal bei Laufenthal im Harz. Neues Jahrbuch für Mineralogie, Monatshefte: 1955: 133-142.

Other Language Names for BornhardtiteHide

German:Bornhardtit

Russian:Борнхардтит

Spanish:Bornhardtita

Relationship of Bornhardtite to other SpeciesHide

Member of:

Bornhardtite Subgroup > Seleniospinel Group > Spinel Supergroup

Other Members of this group:

Trüstedtite

Ni₃Se₄

Iso.

Common AssociatesHide

Associated Minerals Based on Photo Data:

1 photo of Bornhardtite associated with Trogtalite

CoSe₂

Related Minerals - Strunz-mindat Grouping Hide

2.DA.	Zaykovite	Rh₃Se₄	Mon. 2/m : B2/m
2.DA.	Grimmite	NiCo₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.	Zolenskyite	FeCr₂S₄	Mon. 2/m : B2/m
2.DA.	Ezochiite	Cu⁺(Rh³⁺Pt⁴⁺)S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Carrollite	CuCo₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Cuproiridsite	(Cu,Fe)Ir₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Cuprorhodsite	(Cu¹⁺_0.5Fe³⁺_0.5)Rh³⁺₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Daubréelite	Fe²⁺Cr³⁺₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Fletcherite	CuNi₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Florensovite	(Cu,Zn)Cr_1.5Sb_0.5S₄	Iso. m3m (4/m 3 2/m)
2.DA.05	Greigite	Fe²⁺Fe³⁺₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Indite	FeIn₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Kalininite	ZnCr₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Linnaeite	Co²⁺Co³⁺₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Malanite	Cu¹⁺(Ir³⁺Pt⁴⁺)S₄	Iso. m3m (4/m 3 2/m)
2.DA.05	Polydymite	Ni²⁺Ni³⁺₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Siegenite	CoNi₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Trüstedtite	Ni₃Se₄	Iso.
2.DA.05	Tyrrellite	Cu(Co³⁺,Ni³⁺)₂Se₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Violarite	Fe²⁺Ni³⁺₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Xingzhongite	Pb²⁺Ir³⁺₂S₄	Iso.
2.DA.05	Cadmoindite	CdIn₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Cuprokalininite	CuCr₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Joegoldsteinite	MnCr₂S₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.05	Nickeltyrrellite	CuNi₂Se₄	Iso. m3m (4/m 3 2/m) : Fd3m
2.DA.10	Rhodostannite	Cu¹⁺(Fe²⁺_0.5Sn⁴⁺_1.5)S₄	Tet. 4/m : I4₁/a
2.DA.10	Toyohaite	Ag¹⁺(Fe²⁺_0.5Sn⁴⁺_1.5)S₄	Tet. 4/m : I4₁/a
2.DA.15	Brezinaite	Cr₃S₄	Mon. 2/m
2.DA.15	Heideite	(Fe,Cr)_1.15(Ti,Fe)₂S₄	Mon. 2/m
2.DA.20	Inaglyite	Cu₃Pb(Ir,Pt)₈S₁₆	Hex.
2.DA.20	Konderite	Cu₃Pb(Rh,Pt,Ir)₈S₁₆	Hex. 6/m : P6/m
2.DA.25	Kingstonite	(Rh,Ir,Pt)₃S₄	Mon. 2/m : B2/m

Other InformationHide

Health Risks:

No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for BornhardtiteHide

Reference List:

Ramdohr, P., Schmitt, M. (1955) Vier neue natürliche Kobaltselenide vom Steinbruch Trogtal bei Laufenthal im Harz. Neues Jahrbuch für Mineralogie, Monatshefte: 1955: 133-142.

Fleischer, M. (1956) New mineral names. American Mineralogist: 41: 164.

Ramdohr, P. (1969) The Ore Minerals and their Intergrowths, Pergamon Press, pp. 1174.

Bosi, F., Biagioni, C., Pasero, M. (2019) Nomenclature and classification of the spinel supergroup. European Journal of Mineralogy: 31: 183-192.

Localities for BornhardtiteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the

symbol to view information about a locality. The

symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed.

- This locality has estimated coordinates. ⓘ - Click for references and further information on this occurrence. ? - Indicates mineral may be doubtful at this locality.

- Good crystals or important locality for species.

- World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). ~~Struck out~~ - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.


Argentina
Mendoza Province Luján de Cuyo department Cacheuta District ⓘ Sierra de Cacheuta	Grundmann, G., & Förster, H. J. (2018). The Sierra de Cacheuta Vein-Type Se Mineralization, Mendoza Province, Argentina. Minerals, 8(4), 127.
ⓘ Cerro de Cacheuta	Handbook of Mineralogy

Canada
Saskatchewan ⓘ Pinky Fault Uranium Deposit	Handbook of Mineralogy

Germany (TL)
Lower Saxony Goslar District Harz (Landkreis Goslar) ⓘ Trogtal Quarries (TL)	Ramdohr, P., Schmitt, M. (1955) Vier neue natürliche Kobaltselenide vom Steinbruch Trogtal bei Laufenthal im Harz. Neues Jahrbuch für Mineralogie, Monatshefte: 1955: 133-142. Am. Mineral. (1956) 41, 164-165 Weiss, S. (1990) Mineralfundstellen Atlas, Deutschland West. Weise Verlag, München, 320 pages. Cabral, A. R., Koglin, N., & Bratz, H. (2012). Gold-bearing ferroselite (FeSe2) from Trogtal, Harz, Germany, and significance of its Co/Ni ratio. Journal of Geosciences, 57(4), 265-272.
Göttingen District Osterode am Harz Lerbach ⓘ Weintraube Mine	Weiss, S. (1990) Mineralfundstellen Atlas, Deutschland West. Weise Verlag, München, 320 pages.
Saxony-Anhalt Mansfeld-Südharz Mansfeld ⓘ Tilkerode mining district	Wittern: "Mineralfundorte in Deutschland", 2001 Tischendorf, G. (1969). Sources of elements in selenide mineralization near Tilkerode (Harz). International Geology Review, 11(11), 1298-1301.

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Bornhardtite