Click on a letter above to view the list of gems.  

Londonite
Current inventory:  0 gems
 

Chemistry:  (K,Cs,Rb)Al₄Be₄(B,Be)₁₂O₂₈

Discovered in 1998;   IMA status: Valid (IMA approved 1999).
Londonite is named in honor of Dr. David London (1953- ), Professor of Geology and Geophysics at the University of Oklahoma, Norman, Oklahoma, USA, for his contributions to the understanding of granite pegmatites.

Classification

Mineral Classification:

Borates

Strunz 8th Ed. ID:

5/L.02-20

Nickel-Strunz 10th Ed. ID:

6.GC.05

6 : BORATES
G : Heptaborates and other megaborates
C : Tekto-dodecaborates

Related to:

Londonite - Rhodizite Series.  The cesium (Cs) analogue of Rhodizite.

Crystal Data

Crystallography:

Isometric - Hextetrahedral

Crystal Habit:

Typically as well-formed dodecahedra and tetrahedra, to 3.5 cm, modified by [001] and [111]

Twinning:

On [111], uncommon.

Physical Properties

Cleavage:

[111] Indistinct, [111] Indistinct, [111] Indistinct

Fracture:

Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

8.0

Density:

3.34 (g/cm³)

Luminescence:

None

Radioactivity:

Barely Detectable, GRapi = 457.11

Other:

Piezoelectric and Pyroelectric

Optical Properties

Color:

Colorless, White, Sulfur Yellow, pale Yellow, pale Yellowish Green

Transparency:

Transparent to Translucent

Luster:

Vitreous

Refractive Index:

1.6935  Isotropic

Birefringence:

0.00 (Isotropic)

Dispersion:

Weak; 0.018

Pleochroism:

None

Occurances

Geological Setting:

An uncommon component of granite pegmatites, in the central zones and in miarolitic cavities.

Common Associations:

Albite, Apatite (Mn-rich), Béhierite, Beryl (Cs-rich), Danburite, Elbaite–Liddicoatite–Schorl, Hambergite, Hafnian Zircon, Manganocolumbite, Manganotantalite, Microcline, Microlite, Quartz, Rhodizite, Spodumene

Type Locality:

Antandrokomby pegmatite, Manandona Valley, Sahatany Pegmatite Field (Mt Bity (Ibity) area), Vakinankaratra Region (Betafo - Antsirabé region), Antananarivo Province, Madagascar

Year Discovered:

1998; IMA approved 1999

View mineral photos:

Londonite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Londonite is a very rare gem that is closely related to and is the cesium (Cs) dominant analogue of Rhodizite. Rhodizite is potassium (K) dominant. Quantitative chemical analysis is required to differentiate between the two so they are often referred to as Rhodizite-Londonite when specimens have not been chemically tested. Londonite was discovered in the Sahatany Pegmatite Field near Mt. Bity in the Manandona Valley, Vakinankaratra Region, Antananarivo Province, Madagascar and is the only current source of facetable material. Londonite is strongly piezoelectric and pyroelectric and is barely radioactive due to its cesium (Cs) and rubidium (Rb) content. The color of greenish-yellow and yellow gems may fade to colorless with prolonged exposure to sunlight.
 

  
Londonite gems for sale:

We have not photographed our Londonite gems yet.  Please check back soon!