Neptunite
A valid IMA mineral species - grandfathered
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About Neptunite
Neptune
Formula:
KNa2Li(Fe2+)2Ti2[Si4O12]2
Colour:
Black
Lustre:
Vitreous
Hardness:
5 - 6
Specific Gravity:
3.19 - 3.23
Crystal System:
Monoclinic
Member of:
Name:
For Neptune, Roman god of the sea, for close association at type locality with aegirine (named after Aegir, a Scandinavian sea god).
The Fe(II) analogue of manganoneptunite.
Minor rock forming mineral. Probably best know as an associated mineral with benitoite.
Visit gemdat.org for gemological information about Neptunite.
Minor rock forming mineral. Probably best know as an associated mineral with benitoite.
Visit gemdat.org for gemological information about Neptunite.Unique Identifiers
Mindat ID:
2883
Long-form identifier:
mindat:1:1:2883:3
GUID
(UUID V4):
(UUID V4):
23c829e5-ba32-4149-9b99-57692bef1ce8
IMA Classification of Neptunite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
KNa2LiFe2+2Ti2Si8O24
First published:
1893
Classification of Neptunite
9.EH.05
9 : SILICATES (Germanates)
E : Phyllosilicates
H : Transitional structures between phyllosilicate and other silicate units
9 : SILICATES (Germanates)
E : Phyllosilicates
H : Transitional structures between phyllosilicate and other silicate units
70.4.1.1
70 : INOSILICATES Column or Tube Structures
4 : Column or Tube Structures with linked chains forming cages
70 : INOSILICATES Column or Tube Structures
4 : Column or Tube Structures with linked chains forming cages
14.9.26
14 : Silicates not Containing Aluminum
9 : Silicates of Ti
14 : Silicates not Containing Aluminum
9 : Silicates of Ti
Mineral Symbols
As of 2021 there are now IMAâCNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference |
|---|---|---|
| Npt | IMAâCNMNC | Warr, L.N. (2021). IMAâCNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Neptunite
Vitreous
Transparency:
Opaque
Colour:
Black
Comment:
Deep blood-red in splinters
Streak:
Cinnamon-brown
Hardness:
5 - 6 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
on {110}
on {110}
Fracture:
Conchoidal
Density:
3.19 - 3.23 g/cm3 (Measured) 3.24 g/cm3 (Calculated)
Optical Data of Neptunite
Type:
Biaxial (+)
RI values:
nα = 1.690 - 1.691 nβ = 1.693 - 1.700 nγ = 1.719 - 1.736
2V:
Measured: 36° to 49°, Calculated: 36° to 56°
Max Birefringence:
δ = 0.029 - 0.045
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
r < v strong
Pleochroism:
Visible
Comments:
X= pale yellow
Y= yellow-orange
Z= red-orange to red-brown
Y= yellow-orange
Z= red-orange to red-brown
Chemistry of Neptunite
Mindat Formula:
KNa2Li(Fe2+)2Ti2[Si4O12]2
Common Impurities:
Ca
Chemical Analysis
Oxide wt%:
| 1 | 2 | |
|---|---|---|
| SiO2 | 51.53 % | 52.29 % |
| TiO2 | 18.13 % | 17.38 % |
| FeO | 10.91 % | 11.92 % |
| MnO | 4.97 % | 2.27 % |
| MgO | 0.49 % | 1.55 % |
| K2O | 4.88 % | 5.58 % |
| Na2O | 9.26 % | 6.81 % |
| CaO | % | 0.62 % |
| Li2O | % | 1.63 % |
| Total: | 100.17 % | 100.05 % |
Sample references:
| ID | Type | Locality | Reference | Notes |
|---|---|---|---|---|
| 1 | Type Specimen | NarssĂąrssuk pegmatite, Narsaarsuk Plateau, Igaliku, Kujalleq, Greenland | Wet-chemical analysis (Flink), analysis incomplete, Li not analyzed | |
| 2 | California State Gem Mine, Santa Rita Peak, San Benito County, California, USA | Microprobe |
Crystallography of Neptunite
Crystal System:
Monoclinic
Class (H-M):
m - Domatic
Space Group:
Bb
Cell Parameters:
a = 16.427(2) Å, b = 12.478(2) Å, c = 9.975(1) Å
β = 115.56(1)°
β = 115.56(1)°
Ratio:
a:b:c = 1.316 : 1 : 0.799
Unit Cell V:
1,844.54 Ă
Âł (Calculated from Unit Cell)
Z:
4
Morphology:
Prismatic crystals
Twinning:
Interpenetrant on {301}
Crystallographic forms of Neptunite
Crystal Atlas:
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Neptunite no.1 - Goldschmidt (1913-1926)
Neptunite no.2 - Goldschmidt (1913-1926)
Neptunite no.3 - Goldschmidt (1913-1926)
Neptunite no.16 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by
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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) |
|---|---|---|---|---|---|---|---|
| 0018847 | Neptunite | Cannillo E, Mazzi F, Rossi G (1966) The crystal structure of neptunite Acta Crystallographica 21 200-208 |  | 1966 | San Benito, California, USA | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.186 Ă | (100) |
| 9.6 Ă | (60) |
| 3.517 Ă | (45) |
| 3.308 Ă | (35) |
| 2.942 Ă | (32) |
| 2.837 Ă | (32) |
| 2.480 Ă | (32) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Geological Setting:
alkaline rocks
Type Occurrence of Neptunite
General Appearance of Type Material:
Crystals from mm-sized up to 3-4 cm large, on aegirine or embedded in feldspar
Place of Conservation of Type Material:
University of Copenhagen, Copenhagen, Denmark.
Associated Minerals at Type Locality:
Reference:
Flink, G. (1893): Om nÄgra mineral frÄn Grönland. Geologiska Föreningen i Stockholms Förhandlingar. 15, 195-208
Synonyms of Neptunite
Other Language Names for Neptunite
Relationship of Neptunite to other Species
Member of:
Other Members of this group:
| Magnesioneptunite | KNa2Li(Mg)2Ti2[Si4O12]2 | Mon. 2/m : B2/b |
| Manganoneptunite | KNa2Li(Mn2+)2Ti2[Si4O12]2 | Mon. m : Bb |
| Rotherkopfite | KNa2Fe2+(Fe2+)2(Ti1.5Fe2+0.5)[Si4O12]2 | Mon. 2/m : B2/b |
| Watatsumiite | KNa2Li(Mn2+)2V4+2[Si4O12]2 | Mon. m : Bb |
Forms a series with:
Common Associates
Associated Minerals Based on Photo Data:
| 499 photos of Neptunite associated with Benitoite | BaTi(Si3O9) |
| 480 photos of Neptunite associated with Natrolite | Na2Al2Si3O10 · 2H2O |
| 169 photos of Neptunite associated with Joaquinite-(Ce) | NaBa2Ce2FeTi2[Si4O12]2O2(OH,F) · H2O |
| 63 photos of Neptunite associated with Crossite | |
| 16 photos of Neptunite associated with Djurleite | Cu31S16 |
| 12 photos of Neptunite associated with Albite | Na(AlSi3O8) |
| 12 photos of Neptunite associated with Aegirine | NaFe3+Si2O6 |
| 10 photos of Neptunite associated with Microcline | K(AlSi3O8) |
| 8 photos of Neptunite associated with Zektzerite | LiNaZrSi6O15 |
| 6 photos of Neptunite associated with Quartz | SiO2 |
Related Minerals - Strunz-mindat Grouping
| 9.EH.05 | Manganoneptunite | KNa2Li(Mn2+)2Ti2[Si4O12]2 |
| 9.EH.05 | Watatsumiite | KNa2Li(Mn2+)2V4+2[Si4O12]2 |
| 9.EH.05 | Magnesioneptunite | KNa2Li(Mg)2Ti2[Si4O12]2 |
| 9.EH.05 | Rotherkopfite | KNa2Fe2+(Fe2+)2(Ti1.5Fe2+0.5)[Si4O12]2 |
| 9.EH.10 | Grumantite | Na(HSi2O5) · H2O |
| 9.EH.15 | Sarcolite | Na4Ca12Al8Si12O46(SiO4,PO4)(OH,H2O)4(CO3,Cl) |
| 9.EH.20 | Ussingite | Na2AlSi3O8OH |
| 9.EH.25 | Leifite | (Na,H2O)Na6[Be2Al2(Al,Si)Si15O39]F2 |
| 9.EH.25 | Telyushenkoite | (Cs,Na,K)Na6[Be2Al3Si15O39]F2 |
| 9.EH.25 | Eirikite | KNa6Be2(Si15Al3)O39F2 |
| 9.EH.30 | Nafertisite | Na3Fe2+10Ti2(Si6O17)2O2(OH)6F(H2O)2 |
| 9.EH.35 | Veblenite | KNa(Fe2+5Fe3+4Mn7)Nb4(Si2O7)2(Si8O22)2O6(OH)10(H2O)3 |
Other Information
Electrical:
Piezoelectric
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Neptunite
mindat.org URL:
https://www.mindat.org/min-2883.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Neptunite
Reference List:
Flink, Gust. (1893) Om nÄgra mineral frÄn Grönland. Geologiska Föreningen i Stockholm Förhandlingar, 15 (4) 195-208 doi:10.1080/11035899309442185
Laird, Jo, Albee, Arden L. (1972) Chemical composition and physical, optical, and structural properties of benitoite, neptunite, and joaquinite. American Mineralogist, 57 (1-2) 85-102
Localities for Neptunite
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
â - 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).
All localities listed without proper references should be considered as questionable.
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Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia