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Niter

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Formula:
KNO3
System:
Orthorhombic
Colour:
Colorless or white, ...
Lustre:
Sub-Vitreous
Hardness:
2
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.

Chemically it is the K-analogue of nitratine.

Classification of Niter

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
5.NA.10

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
13.2

13 : Nitrates
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http://www.mindat.org/min-2917.html
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Occurrences of Niter

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.

Physical Properties of Niter

Sub-Vitreous
Diaphaneity (Transparency):
Transparent
Colour:
Colorless or white, light yellow, very light gray
Streak:
White
Hardness (Mohs):
2
Tenacity:
Brittle
Cleavage:
Very Good
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)

Crystallography of Niter

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Pmma
Cell Parameters:
a = 5.414Å, b = 9.164Å, c = 6.431Å
Ratio:
a:b:c = 0.591 : 1 : 0.702
Unit Cell Volume:
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
X-Ray Powder Diffraction Data:
d-spacingIntensity
4.66(20)
3.78 (100)
3.73 (60)
3.03 (60)
2.76 (30)
2.71 (20)
2.66 (40)
2.65 (60)
Comments:
5-377 (synthetic)

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
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Dispersion:
r
Optical Extinction:
Parallel
Pleochroism:
Non-pleochroic

Chemical Properties of Niter

Formula:
KNO3
Essential elements:
All elements listed in formula:
Common Impurities:
Na,Li

Relationship of Niter to other Species

Common Associates:
13.1NitratineNaNO3
13.3GerhardtiteCu2(NO3)(OH)3
13.4NitromagnesiteMg(NO3)2 · 6H2O
13.5NitrocalciteCa(NO3)2 · 4H2O
13.6NitrobariteBa(NO3)2
13.7ButtgenbachiteCu19(NO3)2(OH)32Cl4 · 2H2O
13.8SveiteKAl7(NO3)4(OH)16Cl2 · 8H2O
13.9DarapskiteNa3(SO4)(NO3) · H2O
13.10HumberstoniteNa7K3Mg2(SO4)6(NO3)2 · 6H2O
13.11Mbobomkulite(Ni,Cu)Al4((NO3)2,SO4)(OH)12 · 3H2O
13.12Hydrombobomkulite(Ni,Cu)Al4((NO3)2,SO4)(OH)12 · 13-14H2O
13.13Nickelalumite(Ni,Cu)Al4(SO4,(NO3)2)(OH)12 · 3H2O

Other Names for Niter

Other Information

Other Information:
Readily soluble in water.
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 Niter

Reference List:
Reuss, F.A. (1803) Lehrbuch der Mineralogie. Leipzig. part 2, volumes 3: 21 (as Salpeter).

Philips (1818): 137 (as Nitrate of Potash).

Leonhard, K.C. (1826) Handbuch der Oryktognosie. second edition, Heidelberg: 247 (as Kalisalpeter).

Naumann, C.F. (1828) Lehrbuch der Mineralogie, Berlin: 261.

Breithaupt, A. (1832) Vollständige Characteristik etc., 2nd. Ed.: 27 (as Kalinitrat).

Miller (1840) Philosophical Magazine and Journal of Science: 17: 38.

Hausmann, J.F.L. (1847) Handbuch der Mineralogie 3 volumes, Göttingen. Second edition, vol. 2, in two parts: 1416.

Breithaupt, A. (1847) Vollständige Handbuch der Mineralogie. Dresden and Leipzig. Vol. 2: 94.

Schrauf (1860) Konigliche Akademie der Wissenschaften, Vienna, Sitzber.: 41: 790.

Retgers (1889) Zeitschrift für Physikalische Chemie, Leipzig, Berlin: 3: 313.

Dana, E.S. (1892) System of Mineralogy, 6th. Edition, New York: 871.

Gossner (1903) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 38: 143.

Günther (1912) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 50: 92 (density - artif. xls.)(abstract).

Haigh (1912) Journal of the American Chemical Society: 34: 1137.

Johnsen (1914) Jahrb. Radioakt. Und Elektronik: 11: 246.

Goldschmidt, V. (1918) Atlas der Krystallformen. 9 volumes, atlas, and text, vol. 5: 3.

Frood and Hall (1919) Union of South Africa Geological Survey Memorandum 14.

Edwards (1930) Zeitschrift für Kristallographie: 154.

Hintze, Carl (1930) Handbuch der Mineralogie. Berlin and Leipzig. 6 volumes: 1 [3A]: 2713.

Merwin (1930) Int. Crit. Tables: 7: 27.

Mansfield and Boardman (1932) U.S. Geological Survey Bulletin 838.

Larsen, E.S. and Berman, H. (1934) The Microscopic Determination of the Nonopaque Minerals, Second edition, USGS Bulletin 848: 152.

Gibbs (1938) Ann. Sc. London: 3: 213.

Northrop (1942) University of New Mexico Bulletin, Geology Series, 6, no. 1: 227.

Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 303.

Janz, G.J. (1980) Molten-salts data as reference-standards for density, surface-tension viscosity and electrical conductance - KNO3 and NaCl. Journal of Physical and Chemical Reference Data: 9: 791-829.

Chem. Geol. (1988): 67: 85.

Internet Links for Niter

Localities for Niter

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