Niter
A valid IMA mineral species - grandfathered
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About Niter
Formula:
KNO3
Colour:
Colorless or white, light yellow, very light gray
Lustre:
Sub-Vitreous
Hardness:
2
Specific Gravity:
2.11 (Calculated)
Crystal System:
Orthorhombic
Name:
Evolved from "neter" or "nether" (Hebraic), which derived from "natar," a substance that effervesces, which corresponds to the "nitron" of the Greeks and the "nitrum" of the Romans.
Niter, potassium nitrate, is found as an efflorescence in hot, dry regions. Also known as saltpeter.
Unique Identifiers
Mindat ID:
2917
Long-form identifier:
mindat:1:1:2917:5
Similar Names
IMA Classification of Niter
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
KN5+O3
Classification of Niter
5.NA.10
5 : CARBONATES (NITRATES)
N : NITRATES
A : Without OH or H2O
5 : CARBONATES (NITRATES)
N : NITRATES
A : Without OH or H2O
Dana 7th ed.:
18.1.2.1
18.1.2.1
18 : NORMAL NITRATES
1 : AXO3·xH2O, where x can equal zero
18 : NORMAL NITRATES
1 : AXO3·xH2O, where x can equal zero
13.2
13 : Nitrates
13 : Nitrates
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 |
|---|---|---|
| Nit | 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 Niter
Sub-Vitreous
Transparency:
Transparent
Colour:
Colorless or white, light yellow, very light gray
Streak:
White
Hardness:
2 on Mohs scale
Tenacity:
Brittle
Cleavage:
Very Good
On {011} nearly perfect; on {010} fairly good; on {110} imperfect.
On {011} nearly perfect; on {010} fairly good; on {110} imperfect.
Parting:
Twin gliding with K1 (110), K2 (130).
Fracture:
Irregular/Uneven, Sub-Conchoidal
Density:
2.11 g/cm3 (Calculated)
Optical Data of Niter
Type:
Biaxial (-)
RI values:
nα = 1.332 nβ = 1.504 nγ = 1.504
2V:
Measured: 7°
Birefringence:
0.172
Max. Birefringence:
δ = 0.172
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:
High (negative)
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:
r
Optical Extinction:
Parallel
Pleochroism:
Non-pleochroic
Chemistry of Niter
Mindat Formula:
KNO3
Elements listed:
Common Impurities:
Na,Li
Crystallography of Niter
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Space Group:
Pmma
Cell Parameters:
a = 5.414 Å, b = 9.164 Å, c = 6.431 Å
Ratio:
a:b:c = 0.591 : 1 : 0.702
Unit Cell V:
319.07 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Massive, granular, earthy, mealy. Crusts, silky tufts, and delicate acicular crystallization. Artificial crystals are prismatic [001].
Twinning:
Common on {110}, frequently as pseudo-hexagonal groupings.
Comment:
Pmcm
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
Remove metal-metal sticks
Display Options
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Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
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2D | Stereo | Red-Blue | Red-Cyan
View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
Stop | Start
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) |
|---|---|---|---|---|---|---|---|
| 0010326 | Niter | Adiwidjaja G, Pohl D (2003) Superstructure of a-phase potassium nitrate Acta Crystallographica C59 i139-i140 |  | 2003 | synthetic | 0 | 293 |
| 0013163 | Niter | Nimmo J K, Lucas B W (1973) A neutron diffraction determination of the crystal structure of alpha-phase potassium nitrate at 25 C and 100 C Journal of Physics C: Solid State Physics 6 201-211 | 1973 | Synthetic | 0 | 293 | |
| 0013162 | Niter | Nimmo J K, Lucas B W (1973) A neutron diffraction determination of the crystal structure of alpha-phase potassium nitrate at 25 C and 100 C Journal of Physics C: Solid State Physics 6 201-211 | 1973 | Synthetic | 0 | 293 | |
| 0009568 | Niter | Nimmo J, Lucas B (1976) The crystal structures of gamma- and beta-KNO3 and the alpha-gamma-beta phase transformations _cod_database_code 1000051 Acta Crystallographica B32 1968-1971 | | 1976 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.66 Å | (20) |
| 3.78 Å | (100) |
| 3.73 Å | (60) |
| 3.03 Å | (60) |
| 2.76 Å | (30) |
| 2.71 Å | (20) |
| 2.66 Å | (40) |
| 2.65 Å | (60) |
Comments:
5-377 (synthetic)
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 48 : Soil leaching zone minerals | <0.6 |
| 52 : Guano- and urine-derived minerals | <0.4 |
| 53 : Other minerals with taphonomic origins | <0.4 |
Geological Setting:
Surface efflorescences in arid regions; in caves or other dry, sheltered places. Also in soils rich in organic materials, especially after rain during hot weather.
Synonyms of Niter
Other Language Names for Niter
French:Potasse nitratée
Latin:Sal petrae
Nitrum (in part)
Nitrum (in part)
Russian:Селитра
Simplified Chinese:钾硝石
Spanish:Salitre
Common Associates
Associations Based on Photo Data:
| 1 photo of Niter associated with Sveite | (K3-x◻x)Al8(NO3)6O8Cl4 · nH2O |
| 1 photo of Niter associated with Fuenzalidaite | K6(Na,K)4Na6Mg10(SO4)12(IO3)12 · 12H2O |
| 1 photo of Niter associated with 'Agate-Jasper' | SiO2 |
| 1 photo of Niter associated with Native Sulphur | S8 |
| 1 photo of Niter associated with Alum-(K) | KAl(SO4)2 · 12H2O |
Related Minerals - Strunz-mindat Grouping
| 5.NA.05 | Nitratine | NaNO3 |
| 5.NA.15 | Gwihabaite | (NH4,K)NO3 |
| 5.NA.20 | Nitrobarite | Ba(NO3)2 |
| 5.NA.25 | Shilovite | Cu(NH3)4(NO3)2 |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 38.6717% | 11,988 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
Fluorescence of Niter
Not fluorescent
Other Information
Notes:
Readily soluble in water.
Health Risks:
DETONATES WITH COMBUSTIBLE SUBSTANCES!!
Internet Links for Niter
mindat.org URL:
https://www.mindat.org/min-2917.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Niter
Localities for Niter
Showing 213 localities.
symbol to view information about a locality.
The Locality List
- 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).
All localities listed without proper references should be considered as questionable.
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Prieska, Siyathemba Local Municipality, Pixley ka Seme District Municipality, Northern Cape, South Africa