Alum-(K) Mineral Data

General Alum-(K) Information

Chemical Formula:

KAl(SO4)2•12(H2O)

Composition:

Molecular Weight = 474.39 gm

Potassium 8.24 % K 9.93 % K₂O

Aluminum 5.69 % Al 10.75 % Al₂O₃

Hydrogen 5.10 % H 45.57 % H₂O

Sulfur 13.52 % S 33.75 % SO₃

Oxygen 67.45 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

KAl(SO₄)₂•12(H₂O)

Environment:

Derived from the oxidation of sulfide minerals and potassium-bearing minerals.

IMA Status:

Valid Species (Pre-IMA) 1875

Locality:

Vesuvius, Italy. Alum Cave, Tennessee, USA. Link to MinDat.org Location Data.

Name Origin:

Named for the element K and the Latin, alumen.

Synonym:

Native Alum

Potash Alum

Potassium-alum - Renamed to Alum-(K) by Mineralogical Record, v39 (2008), p131

Alum-(K) Image

Images:

Alum-(K)

Comments: White encrustations and ballshaped aggregates of potassium alum.
Location: Scholler mine, Libusin, Kladno, Czech Republic. Scale: See Fingers for Scale.
© Diederik Visser

Alum-(K) Crystallography

Cell Dimensions:

a = 12.133, Z = 4; V = 1,786.10 Den(Calc)= 1.76

Crystal System:

Isometric - DiploidalH-M Symbol (2/m 3) Space Group: P a3

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

By Intensity(I/I_o): 4.298(1), 3.25(0.55), 4.053(0.45),

Crystal Structure:

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Nyburg S C , Steed J , Aleksovska S , Petrusevski V M , Acta Crystallographica, Section B , 56 (2000) p.204-209, Structure of the alums. I. On the sulfate group disorder in the alpha-alums, Locality: synthetic, Sample: T = 173 K

Physical Properties of Alum-(K)

Cleavage:

{111} Indistinct

Color:

Colorless, White.

Density:

1.76

Diaphaneity:

Transparent

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

Water Soluble - Water soluble mineral.

Hardness:

2 - Gypsum

Luminescence:

Non-fluorescent.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Alum-(K)

Gladstone-Dale:

CI meas= -0.004 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.004 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2574,KPDmeas= 0.2574,KC= 0.2564
Ncalc = 1.45

Optical Data:

Isotropic, n=1.453.

Calculated Properties of Alum-(K)

Electron Density:

Bulk Density (Electron Density)=1.84 gm/cc
note: Specific Gravity of Alum-(K) =1.76 gm/cc.

Fermion Index:

Fermion Index = 0.0013552227
Boson Index = 0.9986447773

Photoelectric:

PE_Alum-(K)= 1.89 barns/electron
U=PE_Alum-(K) x r_electron= 3.47 barns/cc.

Radioactivity:

GRapi = 124.32 (Gamma Ray American Petroleum Institute Units)
Concentration of Alum-(K) per GRapi unit = 0.80 (%)

Estimated Radioactivity from Alum-(K) - barely detectable

Alum-(K) Classification

Dana Class:

29.05.05.01 (29)Hydrated Acid and Sulfates

(29.05)where A B (XO4)2 · x(H2O)

(29.05.05)Alum Group

29.05.05.01 Alum-(K) KAl(SO4)2•12(H2O) P a3 2/m 3

29.05.05.02 Alum-(Na) NaAl(SO4)2•12(H2O) P a3 2/m 3

29.05.05.03 Tschermigite (NH4)Al(SO4)2•12(H2O) P a3 2/m 3

29.05.05.04 Lonecreekite (NH4)(Fe,Al)(SO4)2•12(H2O) P a3 2/m 3

29.05.05.05 Lanmuchangite! TlAl(SO4)2•12(H2O) P a3 2/m 3

Strunz Class:

07.CC.20 07 - SULFATES (SELENATES, TELLURATES)

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

07.CC -With medium-sized and large cations

07.CC.20 Lonecreekite (NH4)(Fe,Al)(SO4)2•12(H2O) P a3 2/m 3

07.CC.20 Alum-(K) KAl(SO4)2•12(H2O) P a3 2/m 3

07.CC.20 Alum-(Na) NaAl(SO4)2•12(H2O) P a3 2/m 3

07.CC.20 Lanmuchangite! TlAl(SO4)2•12(H2O) P a3 2/m 3

07.CC.20 Tschermigite (NH4)Al(SO4)2•12(H2O) P a3 2/m 3

Other Alum-(K) Information

References:

NAME( Dana7) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Dana7)

See Also:

Links to other databases for Alum-(K) :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - GeoScienceWorld
4 - Google Images
5 - Google Scholar
6 - MinDAT
7 - Mineralienatlas (Deutsch)
8 - Online Mineral Museum
9 - QUT Mineral Atlas
10 - Ruff.Info

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Print or Cut-and-Paste your Alum-(K) Specimen Label here :

Alum-(K)

KAl(SO4)2•12(H2O)
Dana No: 29.05.05.01 Strunz No: 07.CC.20
Locality:

Notes: