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Lorenzo Romano Amedeo Carlo Avogadro di Quaregna (Quaregga) e di Cerreto
Colourless to white, ...
For Amadeo Avogadro (Turin August 9 1776 - Turin, July 9 1856), Professor of Physics at the University of Turin, Turin, Italy. Remembered for Avogadro's gas law and Avogadro's number.
This page provides mineralogical data about Avogadrite.

Classification of Avogadrite

Approved, 'Grandfathered' (first described prior to 1959)

C : Complex halides
A : Borofluorides

2 : AmBX4

8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
12 : Fluorborates (BF'4) and fluosilicates (SiF''6)

Physical Properties of Avogadrite

Diaphaneity (Transparency):
Colourless to white, yellowish to reddish when impure, colourless in transmitted light
2.9 g/cm3 (Calculated)

Optical Data of Avogadrite

Biaxial (-)
RI values:
nα = 1.324 nβ = 1.325 nγ = 1.325
Measured: 75° , Calculated: 58°
Max Birefringence:
δ = 0.001
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
r > v, strong

Chemical Properties of Avogadrite

IMA Formula:
Elements listed in formula:
Analytical Data:
Partial analysis of material from Vesuvius, Italy, determined on aqueous extracts from mixtures of sublimates.
K (15.2)
Cs (7.0)
B (12.0)

Crystallography of Avogadrite

Crystal System:
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Cell Parameters:
a = 8.6588 Å, b = 5.48 Å, c = 7.0299 Å
a:b:c = 1.58 : 1 : 1.283
Unit Cell Volume:
V 333.57 ų (Calculated from Unit Cell)
Octagonal crystals, tabular to platy on {001}, may be elongated along [010] or [100].
X-Ray Powder Diffraction Data:
3.41 (100)
3.26 (80)
3.06 (75)
2.068 (55)
3.51 (45)
2.801 (40)
2.091 (35)
X-ray data of synthetic K[BF4] (ICDD 16-378)

Occurrences of Avogadrite

Type Occurrence of Avogadrite

General Appearance of Type Material:
minute octagonal crystals and dense crusts
Place of Conservation of Type Material:
Natural History Museum, Paris, France (No. 126.148)
Geological Setting of Type Material:
Sublimation products around volcanic fumaroles
Associated Minerals at Type Locality:

Relationship of Avogadrite to other Species


Other Names for Avogadrite

Name in Other Languages:

Other Information

Thermal Behaviour:
The mineral becomes cubic above 273°C.
Other Information:
Slightly soluble in water.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Avogadrite

Reference List:
Carobbi (1926) Reale accademia nazionale dei Lincei, Rome, Rend.: (6), 4, 382.

Zambonini (1926) Reale accademia nazionale dei Lincei, Rome, Rend.: (6), 3, 644.

Zambonini and Coniglio (1926) Reale accademia nazionale dei Lincei, Rome, Rend.: (6), 3, 521.

American Mineralogist (1927) 12, 232.

Pesce (1930) Gazzetta chimica italiana, Rome: 60: 936.

Finbak and Hassel (1936) Zeitschrift für Physikalische Chemie, Leipzig, Berlin: 32: 433 (isometric polymorph).

Klinkenberg (1937) Recueil des travaux chimiques des Pays-Bas et de la Belgique, Leyden: 56: 36.

Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 97-98.

Vlasov, K. A., Ed. (1966): Mineralogy of rare elements, Vol. 2, 65-66.

Brunton, G. (1969): The crystal structure of KBF4. Acta Crystallographica 25, 2161-2162.

Anthony, J. W. et al. (1997): Handbook of Mineralogy, Vol. 3, 32.

Internet Links for Avogadrite URL:
Please feel free to link to this page.

Localities for Avogadrite

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Italy (TL)
  • Campania
    • Naples Province
      • Somma-Vesuvius Complex
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 98.
Russo, M., Punzo, I. (2004): I minerali del Somma-Vesuvio, AMI
  • Sicily
    • Messina Province
      • Eolie Islands (Aeolian Islands)
        • Lipari
          • Vulcano Island
GRAMACCIOLI, C.M., CAMPOSTRINI, I. (2007): Demartinite, a new natural polymorph of K2SiF6 from La Fossa crater, Vulcano, Aeolian Islands, Italy. - Canadian Mineralogist - 45, 1275-1280.
  • Far-Eastern Region
Anthony, J. W. et al. (1997): Handbook of Mineralogy, Vol. 3, 32
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