Lecontite Mineral Data

General Lecontite Information

Chemical Formula:

(NH4,K)Na(SO4)•2(H2O)

Composition:

Molecular Weight = 178.39 gm

Potassium 5.48 % K 6.60 % K₂O

Sodium 12.89 % Na 17.37 % Na₂O

Hydrogen 1.70 % H - % Calc as (NH₄)₂O

Hydrogen 2.26 % H 20.20 % H₂O

Sulfur 17.98 % S 44.88 % SO₃

Nitrogen 5.89 % N 10.95 % (NH₄)₂O

Oxygen 53.81 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

(NH₄)_0.75K_0.25Na(SO₄)•2(H₂O)

Environment:

Early product of the breakdown of bat guano.

IMA Status:

Valid Species (Pre-IMA) 1858

Locality:

Las Piedras Cave, near Comayagua, 62 km northwest of Tegucigalpa, Honduras. Link to MinDat.org Location Data.

Name Origin:

Named for John Lawrence LeConte (1825-1883), American entomologist, University of California, Berkeley, California, USA, who discovered the mineral.

Name Pronunciation:

Lecontite + Pronunciation

Synonym:

ICSD 77896

PDF 15-283

Lecontite Image

Images:

Lecontite Mascagnite

Comments: SEM BSE image of fine-grained lecontite (Le) and thenardite, occupying the space between mascagnite (M) crystals. CanMin 47:573.
Location: Coal-waste heap in Avion, northern France, that has been undergoing subsurface combustion for several decades. Scale: See Image.
© Canadian Mineralogist

Lecontite Crystallography

Axial Ratios:

a:b:c =0.6412:1:0.4856

Cell Dimensions:

a = 8.24, b = 12.85, c = 6.24, Z = 4; V = 660.72 Den(Calc)= 1.79

Crystal System:

Orthorhombic - Disphenoidal H-M Symbol (2 2 2) Space Group: P 2₁2₁2₁

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 5.068(1), 3.802(0.94), 3.033(0.89),

Physical Properties of Lecontite

Cleavage:

{011} Distinct

Color:

Colorless.

Density:

1.745

Diaphaneity:

Transparent

Hardness:

2-2.5 - Gypsum-Finger Nail

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Lecontite

Gladstone-Dale:

CI meas= -0.328 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= -0.295 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2512,KPDmeas= 0.2577,KC= 0.1941
Ncalc = 1.34 - 1.35

Optical Data:

Biaxial (-), a=1.44, b=1.454, g=1.455, bire=0.0150, 2V(Calc)=28, 2V(Meas)=29.74.

Calculated Properties of Lecontite

Electron Density:

Bulk Density (Electron Density)=1.85 gm/cc
note: Specific Gravity of Lecontite =1.79 gm/cc.

Fermion Index:

Fermion Index = 0.06
Boson Index = 0.94

Photoelectric:

PE_Lecontite= 1.87 barns/electron
U=PE_Lecontite x r_electron= 3.46 barns/cc.

Radioactivity:

GRapi = 81.53 (Gamma Ray American Petroleum Institute Units)
Concentration of Lecontite per GRapi unit = 1.23 (%)

Estimated Radioactivity from Lecontite - barely detectable

Lecontite Classification

Dana Class:

29.02.01.01 (29)Hydrated Acid and Sulfates

(29.02)where (A+)2 XO4 � x(H2O)

(29.02.01)Dana Group

29.02.01.01 Lecontite (NH4,K)Na(SO4)•2(H2O) P 2₁2₁2₁ 2 2 2

Strunz Class:

07.CD.15 07 - SULFATES (SELENATES, TELLURATES)

07.C - Sulfates (selenates, etc.) without Additional Anions, with H2O

07.CD -With only large cations

07.CD.15 Lecontite (NH4,K)Na(SO4)•2(H2O) P 2₁2₁2₁ 2 2 2

Other Lecontite Information

References:

NAME( AntBidBlaNic5) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

Links to other databases for Lecontite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info
15 - WWW-MINCRYST

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Print or Cut-and-Paste your Lecontite Specimen Label here :

Lecontite

(NH4,K)Na(SO4)•2(H2O)
Dana No: 29.02.01.01 Strunz No: 07.CD.15
Locality:

Notes:

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