# Mellite
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> Source: https://en.wikipedia.org/wiki/Mellite
> Source revision: 1266277426
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{{Short description|Organic mineral}}
{{distinguish|Melilite}}
{{Infobox mineral
| name = Mellite
| boxwidth =
| boxbgcolor =#7c5745
| boxtextcolor = #fff
| image = Mellite-177555.jpg
| imagesize = 260px
| alt =
| caption =
| category = [Organic minerals](/source/Organic_minerals)
| formula = Al2[C6(COO)6]·16H2O
| IMAsymbol = Mel[{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}]
| molweight =
| strunz = 10.AC.05
| dana =
| system = [Tetragonal](/source/Tetragonal)
| class = Ditetragonal dipyramidal (4/mmm)
[H-M symbol](/source/H-M_symbol): (4/m 2/m 2/m)
| symmetry = ''I4''1/acd
| unit cell = a = 15.53 Å, c = 23.19 Å; Z = 8
| color = Honey-yellow, deep red, pale shades of red, brown, gray, white;
| colour =
| habit = Elongated bipyramidal prismatic; as nodules and coatings, fine-grained massive
| twinning =
| cleavage = poor/indistinct on {023}
| fracture = conchoidal
| tenacity = Slightly sectile
| mohs = 2–{{frac|2|1|2}}
| luster = Vitreous, resinous, greasy
| streak = White
| diaphaneity = Transparent to translucent
| gravity = 1.64
| density =
| polish =
| opticalprop = Uniaxial (−) may be anomalously biaxial
| refractive = nω = 1.539 nε = 1.511
| birefringence = δ = 0.028
| pleochroism = Weak; O = yellowish brown; E = yellow
| 2V =
| dispersion =
| extinction =
| length fast/slow =
| fluorescence = Pale yellow to blue (LW & SW UV)
| absorption =
| melt =
| fusibility =
| diagnostic =
| solubility =
| impurities =
| alteration =
| other = [Pyroelectric](/source/Pyroelectricity)
| prop1 =
| prop1text =
| references = [
}}
'''Mellite''', also called '''honeystone''', is an unusual [mineral](/source/mineral) being also an [organic chemical](/source/organic_chemical). It is chemically identified as an [aluminium](/source/aluminium) salt of [mellitic acid](/source/mellitic_acid), and specifically as aluminium benzenehexacarboxylate hexadeca[hydrate](/source/hydrate), with the [chemical formula](/source/chemical_formula) Al2C6(COO)6·16H2O.][http://webmineral.com/data/Mellite.shtml Webmineral data]
It is a translucent [honey](/source/honey)-coloured [crystal](/source/crystal) which can be polished and [facet](/source/facet)ed to form striking [gemstone](/source/gemstone)s. It crystallizes in the [tetragonal](/source/tetragonal) system and occurs both in good crystals and as formless masses. It is soft with a [Mohs hardness](/source/Mohs_hardness) of 2 to 2.5 and has a low [specific gravity](/source/specific_gravity) of 1.6.[http://rruff.geo.arizona.edu/doclib/hom/mellite.pdf Handbook of Mineralogy][
It was discovered originally in 1789 at [Artern](/source/Artern) in [Thuringia](/source/Thuringia), [Germany](/source/Germany). It has subsequently also been found in [Russia](/source/Russia), [Austria](/source/Austria), the [Czech Republic](/source/Czech_Republic), and [Hungary](/source/Hungary). It was named from the Greek {{lang|grc|μέλι}} ''meli'' "honey",][{{LSJ|me/li^|μέλι|ref}}.] in allusion to its color.[{{Cite web|url=http://www.mindat.org/min-2638.html|title = Mellite}}]
It is found associated with [lignite](/source/lignite) and is assumed to be formed from [plant](/source/plant) material with aluminium derived from [clay](/source/clay).[
thumb|center|Cut and polished mellite gemstone
==Structure==
The [crystal structure](/source/crystal_structure) of mellite has been determined by [neutron diffraction](/source/neutron_diffraction) and consists of slightly distorted Al(H2O)63+ [octahedra](/source/Octahedral_molecular_geometry) linked by [hydrogen bond](/source/hydrogen_bond)s to [C6(COO)6]6− [mellitate](/source/mellitic_acid) anions and [water of crystallization](/source/water_of_crystallization).][{{ cite journal | first1 = Christian | last1 = Robl | first2 = Werner F. | last2 = Kuhs | title = A neutron diffraction study on hydrogen bonding in the mineral mellite (Al2[C6(COO)6] · 16H2O) at 15 K | journal = [J. Solid State Chem.](/source/Journal_of_Solid_State_Chemistry) | year = 1991 | volume = 92 | issue = 1 | pages = 101–109 | doi = 10.1016/0022-4596(91)90246-E | bibcode = 1991JSSCh..92..101R }}]
File:Mellite-asymmetric-unit-from-xtal-3D-bs-17.png|[Ball-and-stick model](/source/Ball-and-stick_model) of the [asymmetric unit](/source/asymmetric_unit) of mellite
File:Mellite-asymmetric-unit-from-xtal-3D-sf.png|[Space-filling model](/source/Space-filling_model) of the asymmetric unit
File:Mellite-3x3x3-unit-cells-from-xtal-3D-sf.png|Packing of 3×3×3 [unit cell](/source/unit_cell)s
==See also==
* [Mellitic anhydride](/source/Mellitic_anhydride)
==References==
{{Commons category| Mellite}}
{{Reflist}}
Category:Aluminium minerals
Category:Organic minerals
Category:Tetragonal minerals
Category:Minerals in space group 142
Category:Luminescent minerals
Category:Minerals described in 1789
{{Mineral-stub}}
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Adapted from the Wikipedia article [Mellite](https://en.wikipedia.org/wiki/Mellite) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Mellite?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.