Londonite Mineral Data

Londonite Mineral Data

General Londonite Information

Chemical Formula:

CsAl4Be4(B,Be)12O28

Composition:

Molecular Weight = 810.52 gm

Cesium 8.20 % Cs 8.69 % Cs₂O

Potassium 1.93 % K 2.32 % K₂O

Rubidium 1.05 % Rb 1.15 % Rb₂O

Beryllium 5.56 % Be 15.43 % BeO

Aluminum 13.32 % Al 25.16 % Al₂O₃

Boron 14.67 % B 47.24 % B₂O₃

Oxygen 55.27 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Cs_0.5K_0.4Rb_0.1Al₄Be₄B₁₁BeO₂₈

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 - Antsirab? 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)= 3.43

Crystal System:

Isometric - HextetrahedralH-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),

Crystal Structure:

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drag2 - RMB Resize/Rotate
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H - Help Screen
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Taxer K J , Buerger M J , Zeitschrift fur Kristallographie , 125 (1967) p.423-436, The crystal struture of rhodizite, Note: name of mineral altered according to IMA decision in 1999, to name the Cs dominant phase: londonite, Locality: Manjaka, Madagascar

Physical Properties of Londonite

Cleavage:

None

Color:

Colorless, White, Yellow.

Density:

3.34

Diaphaniety:

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= -0.002 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.024 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.202,KPDmeas= 0.2075,KC= 0.2071

Optical Data:

Isotropic, n=1.693.

Calculated Properties of Londonite

Electron Density:

r_electron=3.21 gm/cc
note: r_Londonite=3.34 gm/cc.

Fermion Index

Fermion Index = 0.08505
Boson Index = 0.91495

Photoelectric:

PE_Londonite= 34.34 barns/electron
U=PE_Londonite x r_electron= 110.34 barns/cc.

Radioactivity:

GRapi = 457.11 (Gamma Ray American Petroleum Institute Units)

Estimated Radioactivity from Londonite - barely detectable

Londonite Classification

Dana Class:

25.8.2.2 (25)Anhydrous Borates Containing Hydroxyl or Halogen

(25.8)Dana Type

(25.8.2)Dana Group

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

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

Strunz Class:

V/L.02-30 V - Nitrates, Carbonates and Borates

V/L - Shelly borates with [BO2]1- to [B6O10]2-

V/L.02 - Hambergite - Rhodizite series

V/L.02-10 Hambergite Be2BO3(OH) P bca 2/m 2/m 2/m

V/L.02-20 Rhodizite (K,Cs)Al4Be4(B,Be)12O28 P 43m 4 3m

V/L.02-30 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 -Google Images 4 -Google Scholar 5 -Handbook of Mineralogy (UofA) 6 -MinDAT 7 -MinMax(Deutsch) 8 -MinMax(English) 9 -Mineralienatlas (Deutsch) 10 -QUT Mineral Atlas

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Londonite

CsAl4Be4(B,Be)12O28
Dana No: 25.8.2.2 Strunz No: V/L.02-30
Locality:

Notes: