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Formula: Al2(OH)5F
Hydroxide, epitaxial on weloganite
Crystal system: Monoclinic
Specific gravity: 2.492 calculated
(Mindat)
2.43 measured and 2.51 calculated for material from the Francon Quarry
(AM 110.5.829)
Hardness: 2 to 3
Streak: White
Colour: Colourless to white
Luminescence: Bluish-white fluorescence under short wave UV (λ=254 nm) and a yellowish-white fluorescence under long
wave UV (λ=350 nm). Also phosphorescent (material from the Francon quarry)
Environments
Sedimentary environments
Hydrothermal environments
Nannoniite has been known as an unnamed gibbsite-like mineral since
1968, and it was not until 2024 that it was approved as a new mineral with the name "nannoniite".
Localities
At the Francon quarry, Montréal, Québec, Canada, in 1979 a gibbsite-like
mineral that was finally identified, in 2024, as nannoniite was found. It was described as chalk-white powdery
coatings, porcelain-like and waxy granular material, white translucent globules and botryoidal crusts and white
shells. The globules are typically 0.1 to 0.2 mm across and consist of radial aggregates. Some glob ules have
coalesced into botryoidal crusts; surface areas of the crusts are generally no more than 1 to
2 mm2, and contamination by dawsonite,
fluorite, calcite and
halloysite is common
(CM 28.1.147-153).
Nannoniite is extremely widespread at the Francon Quarry and is present on or associated with most samples of
weloganite
(AM 110.5.829).
Nannoniite from the Francon Quarry -
Image
At the type locality, Le Cetine di Cotorniano Mine, Chiusdino, Siena Province, Tuscany, Italy, the unnamed mineral
first reported from the Francon Quarry in Canada and formerly known as “UM1990-28:OHF:Al” has been approved under the
name nannoniite. This mineral was first reported in 1968 in the type description of
weloganite as an unidentified mineral that yielded a powder X-ray
diffraction pattern similar to that of gibbsite. Although nannoniite
is presently (May 2025) known from just four localities, it is relatively common at two of them, the Francon quarry
and Le Cetine di Cotorniano Mine; it is widespread in cavities within silicified
limestone at the Italian type locality
(AM110.5.829).
Nannoniite occurs as (hemi-)spherical aggregates, up to 1 mm in diameter, formed by spindle-like crystals or
tabular individuals. Associated minerals include alunite,
baryte, gypsum and
quartz
(Mindat).
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