Menilite
A rock subtype
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About Menilite
Name:
Named after locality.
Opaline concretions found in marls, gypsums and shales. Sometimes considered a variety of opal but probably impure and really just young Flint nodules which haven’t recrystallised to quartz yet; thus really a rock rather than a mineral.
Originally reported from Ménilmontant, Paris, Ile-de-France, France as nodules in the shale (Menilite formation?) (de Saussure, 1795). The analysis gives 10% water/organic matter.
Note: The name is also used informally for a bituminous shale with chert beds from the Menilite Formation (Eocene/Oligocene).
Jameson's System of Mineralogy from 1816 says that Menilite was divided by Hoffmann into two sub-species - "Brown Menilite" and "Grey Menilite":
Brown Menilite = Leberopal (liver opal)
Color: Chestnut-brown, sometimes inclines to liver brown. On the surface it has sometimes a bluish colour.
Always occurs tuberose, seldom larger than a fist, often smaller. External surface rough and dull.
The Spanish "menilitas", which are by far the most abundant ones in collections, occur in a diatomaceous earth deposit. The nodules consist of light toffee-brown to pale grey massive opal, with abundant inclusions of diatoms (themselves composed of opal) from the host rock, with a white chalky exterior of powdery opal, so three "varieties" of opal in a single nodule. The interiors are hard and compact and take a good polish, so sometimes used for opaque lapidary work.
Grey Menilite = Grauer Menilite (of Hoffmann)
Yellowish-grey sometimes inclining to wood-brown.
Tuberose but more compressed than the brown subspecies, and the external surface is smoother.
Occurs at Argenteuil near Paris embedded in clayey marl and gypsum.
Originally reported from Ménilmontant, Paris, Ile-de-France, France as nodules in the shale (Menilite formation?) (de Saussure, 1795). The analysis gives 10% water/organic matter.
Note: The name is also used informally for a bituminous shale with chert beds from the Menilite Formation (Eocene/Oligocene).
Jameson's System of Mineralogy from 1816 says that Menilite was divided by Hoffmann into two sub-species - "Brown Menilite" and "Grey Menilite":
Brown Menilite = Leberopal (liver opal)
Color: Chestnut-brown, sometimes inclines to liver brown. On the surface it has sometimes a bluish colour.
Always occurs tuberose, seldom larger than a fist, often smaller. External surface rough and dull.
The Spanish "menilitas", which are by far the most abundant ones in collections, occur in a diatomaceous earth deposit. The nodules consist of light toffee-brown to pale grey massive opal, with abundant inclusions of diatoms (themselves composed of opal) from the host rock, with a white chalky exterior of powdery opal, so three "varieties" of opal in a single nodule. The interiors are hard and compact and take a good polish, so sometimes used for opaque lapidary work.
Grey Menilite = Grauer Menilite (of Hoffmann)
Yellowish-grey sometimes inclining to wood-brown.
Tuberose but more compressed than the brown subspecies, and the external surface is smoother.
Occurs at Argenteuil near Paris embedded in clayey marl and gypsum.
Unique Identifiers
Mindat ID:
9796
Long-form identifier:
mindat:1:1:9796:9
GUID
(UUID V4):
(UUID V4):
718107bf-c750-4e1e-8220-28b33c996cc1
Classification of Menilite
Crystallography of Menilite
Morphology:
Concretionary
Other Language Names for Menilite
Common Associates
Associated Minerals Based on Photo Data:
6 photos of Menilite associated with Opal | SiO2 · nH2O |
2 photos of Menilite associated with Hydrophane | SiO2 · nH2O |
2 photos of Menilite associated with Gypsum | CaSO4 · 2H2O |
1 photo of Menilite associated with Nontronite | Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
1 photo of Menilite associated with Chalcedony | SiO2 |
Internet Links for Menilite
mindat.org URL:
https://www.mindat.org/min-9796.html
Please feel free to link to this page.
Please feel free to link to this page.
References for Menilite
Reference List:
Localities for Menilite
Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
Struck out - Mineral was erroneously reported from this locality.
Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).
All localities listed without proper references should be considered as questionable.
All localities listed without proper references should be considered as questionable.
Algeria | |
| Rocks & Min.: 17:243. |
France | |
| Belot (1978) |
Delamétherie (1795) | |
| Belot (1978) |
Japan | |
| Hiroaki Tano specimens |
Hiroaki Tano's specimen | |
Morocco | |
| Jewel Tunnel specimens obtained by Rock ... |
Poland | |
| Personally collected by Zając Piotr in ... |
Spain | |
| Calvo (2016) |
| Juan Miguel Casanova Honrubia ... |
| found by Frank de Wit 2008 |
INTAN specimens (Barcelona) | |
MTI Mineralogía Topográfica Ibérica | |
| Joaquim Mollfulleda |
Albacete, Castile-La Mancha, Spain