Lucabindiite is a

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...

discovered in 1998 from the La Fossa crater at

Vulcano Vulcano ( scn, Vurcanu) or Vulcan is a small volcanic island belonging to Italy in the Tyrrhenian Sea, about north of Sicily and located at the southernmost end of the seven Aeolian Islands. The island is known for its volcanic activity and c ...

, the Aeolian islands off the coast of

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...

. It has the chemical formula ( and is hexagonal. After months of collecting sublimates and encrustations, the researchers discovered lucabindiite which was found on the surface of pyroclastic

breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...

. The mineral is named after

Luca Bindi Luca Bindi (born 1971) is an Italian geologist. He holds the Chair of Mineralogy and Crystallography and is the Head of the Department of Earth Sciences of the University of Florence. He is also a research associate at the Istituto di Geoscienze e ...

, who was a professor of

mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the proces ...

and former head of the Division of Mineralogy of the Natural History Museum of the

University of Florence The University of Florence (Italian: ''Università degli Studi di Firenze'', UniFI) is an Italian public research university located in Florence, Italy. It comprises 12 schools and has around 50,000 students enrolled. History The first universi ...

Occurrence and physical properties

The researchers discovered a minute amount of crystals of lucabindiite, therefore they could not perform a direct measurement of the refractive index. However, two other methods, Mandarino method (1981) and Korotkov–Atuchin method (2008), were used to estimate the average

refractive index In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

. These values are 1.92 and 1.88, respectively. The small amount they obtained made it difficult or impossible to measure other physical properties. The

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

was calculated at 3.68 g/cm³. The mineral is very brittle, shows no signs of cleavage, parting or fracture patterns, and hardness was not determined. Lucabindiite is formed by the occurrence of steam of hydrogen halogenides, and arsenic. Lucabiindite is also found in conjunction with

arsenolite Arsenolite is an arsenic mineral, chemical formula As4O6. It is formed as an oxidation product of arsenic sulfides. Commonly found as small octahedra it is white, but impurities of realgar or orpiment may give it a pink or yellow hue. It can be a ...

, K and NH₄ halides,

orpiment Orpiment is a deep-colored, orange-yellow arsenic sulfide mineral with formula . It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of another a ...

realgar Realgar ( ), also known as "ruby sulphur" or "ruby of arsenic", is an arsenic sulfide mineral with the chemical formula α-. It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in assoc ...

, kirkiite, and vurroite. Lucabindiite has a structure containing (001) layers of neutral sheets. Each sheet is formed by pyramids and is connected by a shared interlayer oxygen.

Chemical and spectroscopic studies

Lucabindiite has the chemical formula (. A quantitative analysis was performed using energy dispersive spectroscopy due to the small sample size of 100 μm smeared on a 30 nm thick film of carbon. The chemical formula obtained from this method is on the basis of 7 anions. The presence of

ammonium The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...

was confirmed using the structure refinement and Fourier-transform infrared spectroscopy. X-ray powder diffraction was performed on lucabindiite and the values calculated are: a = 5.2372(2)Å, c = 9.0085(7)Å, V = 213.98(2)Å³.

References

# Garavelli, A., Mitolo, D., Pinto, D., Vurro, F. (2013): Lucabindiite, ({{chem, K,NH4)As4O6(Cl,Br), a new

fumarole mineral Fumarole minerals are minerals which are deposited by fumarole exhalations. They form when gases and compounds desublimate or precipitate out of condensates, forming mineral deposits. They are mostly associated with volcanoes (as volcanic sublimat ...

from the "La Fossa" crater at Vulcano, Aeolian Islands, Italy. American Mineralogist, 98, 470–477. # Mandarino, J.A. (1981) The Gladstone-Dale relationship. IV. The compatibility index and its application. Canadian Mineralogist, 19, 441–450. # Korotkov, A.S. and Atuchin, V.V. (2008) Prediction of refractive index of inorganic compounds by chemical formula. Optics Communications, 281, 2132–2138. Arsenic minerals Hexagonal minerals Minerals in space group 191

Occurrence and physical properties

Chemical and spectroscopic studies

See also

References