Londonite Mineral Data

General Londonite Information

Chemical Formula:

CsAl4Be4(B,Be)12O28

Composition:

Molecular Weight = 808.60 gm

Cesium 7.89 % Cs 8.36 % Cs₂O

Potassium 1.84 % K 2.21 % K₂O

Rubidium 0.95 % Rb 1.04 % Rb₂O

Sodium 0.09 % Na 0.11 % Na₂O

Lithium 0.02 % Li 0.04 % Li₂O

Calcium 0.10 % Ca 0.14 % CaO

Manganese 0.07 % Mn 0.09 % MnO

Beryllium 5.57 % Be 15.47 % BeO

Aluminum 13.28 % Al 25.09 % Al₂O₃

Iron 0.07 % Fe 0.09 % FeO

Silicon 0.03 % Si 0.07 % SiO₂

Boron 14.69 % B 47.31 % B₂O₃

Oxygen 55.40 % O

______ ______

100.00 % 100.03 % = TOTAL OXIDE

Empirical Formula:

Cs_0.48K_0.38Rb_0.09Na_0.03Ca_0.02Mn²⁺_0.01Al_3.98Li_0.02Fe²⁺_0.01Be₄B_10.99Si_0.01BeO₂₈

Environment:

Found in miarolitic cavities. Cs-analogue of rhodizite.

IMA Status:

Approved IMA 1999 (Dana # Added)

Locality:

Central units or the Antandrokomby, Antsonombato, and Ampanivana granitic pegmatites in Central Madagascar. Link to MinDat.org Location Data.

Name Origin:

Named for David London (1953-), petrologist at the University of Oklahoma, Oklahoma, USA.

Synonym:

IMA1999-014

Londonite Image

Images:

Londonite

Comments: A dodecahedral crystal of londonite.
Location: Antandrokomby pegmatite, Manandona valley, Sahatany Valley, Betafo - AntsirabÃ© region, Antananarivo Province, Madagascar. Scale: Crystal size 7 mm.
© Thomas Witzke / Abraxas-Verlag

Images:

Londonite

Comments: A yellow , lustrous, well developed londonite crystal 1.2 cm. on matrix.
Location: Antandrokomby, Sahatany valley, Madagascar. Scale: Crystal size 1.2 cm.
© Sandro Maggia/Minernet.it

Londonite Crystallography

Cell Dimensions:

a = 7.3205, Z = 1; V = 392.30 Den(Calc)= 3.42

Crystal System:

Isometric - Hextetrahedral H-M Symbol (4 3m) Space Group: P 43m

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

By Intensity(I/I_o): 2.9898(1)(211), 2.1132(0.7)(222), 2.441(0.5)(300,221),1.7759(0.4)(410,322), 1.9568(0.35)(321), 3.276(0.35)(210), 2.208(0.3),

Physical Properties of Londonite

Cleavage:

None

Color:

Colorless, White, Yellow.

Density:

3.34

Diaphaneity:

Transparent

Fracture:

Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.

Habit:

Euhedral Crystals - Occurs as well-formed crystals showing good external form.

Hardness:

8 - Topaz

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Londonite

Gladstone-Dale:

CI meas= 0 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.024 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2026,KPDmeas= 0.2075,KC= 0.2075
Ncalc = 1.69 - 1.71

Optical Data:

Isotropic, n=1.693.

Calculated Properties of Londonite

Electron Density:

Bulk Density (Electron Density)=3.21 gm/cc
note: Specific Gravity of Londonite =3.34 gm/cc.

Fermion Index:

Fermion Index = 0.08
Boson Index = 0.92

Photoelectric:

PE_Londonite= 33.04 barns/electron
U=PE_Londonite x r_electron= 106.21 barns/cc.

Radioactivity:

GRapi = 413.95 (Gamma Ray American Petroleum Institute Units)
Concentration of Londonite per GRapi unit = 0.24 (%)

Estimated Radioactivity from Londonite - barely detectable

Londonite Classification

Dana Class:

25.08.02.02 (25)Anhydrous Borates Containing Hydroxyl or Halogen

(25.08)Dana Type

(25.08.02)Dana Group

25.08.02.01 Rhodizite (K,Cs)Al4Be4(B,Be)12O28 P 43m 4 3m

25.08.02.02 Londonite! CsAl4Be4(B,Be)12O28 P 43m 4 3m

Strunz Class:

06.GC.05 06 - BORATES

06.G - Heptaborates and other Megaborates

06.GC -Tekto-dodecaborates

06.GC.05 Rhodizite (K,Cs)Al4Be4(B,Be)12O28 P 43m 4 3m

06.GC.05 Londonite! CsAl4Be4(B,Be)12O28 P 43m 4 3m

Other Londonite Information

References:

NAME( AmMin, Vol 87, p 356) PHYS. PROP.(AmMin, Vol 87, p 356) OPTIC PROP.(AmMin, Vol 87, p 356)

See Also:

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

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

Londonite

CsAl4Be4(B,Be)12O28
Dana No: 25.08.02.02 Strunz No: 06.GC.05
Locality:

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