Mellite, also called honeystone, is an unusual mineral being also an organic chemical. It is chemically identified as an aluminium salt of mellitic acid, and specifically as aluminium benzene hexacarboxylate

hydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

, with the chemical formula Al₂C₆(COO)₆·16H₂O.http://webmineral.com/data/Mellite.shtml Webmineral data It is a translucent

honey Honey is a sweet and viscous substance made by several bees, the best-known of which are honey bees. Honey is made and stored to nourish bee colonies. Bees produce honey by gathering and then refining the sugary secretions of plants (primar ...

-coloured crystal which can be polished and faceted to form striking

gemstone A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, ...

s. It crystallizes in the tetragonal system and occurs both in good crystals and as formless masses. It is soft with a Mohs hardness of 2 to 2.5 and has a low 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 Artern is a town in the Kyffhäuserkreis district, Thuringia, Germany. The former municipalities Heygendorf and Voigtstedt were merged into Artern in January 2019. Geography Artern is situated at the confluence of the rivers Unstrut and Helme, ...

in Thuringia, Germany. It has subsequently also been found in Russia, Austria, the Czech Republic, and Hungary. It was named from the Greek ''meli'' "honey", in allusion to its color. It is found associated with

lignite Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...

and is assumed to be formed from plant material with aluminium derived from clay. MELLITE Taillée Hongrie

Structure

The crystal structure of mellite has been determined by neutron diffraction and consists of slightly distorted Al(H₂O)₆³⁺ octahedra linked by

hydrogen bond In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a ...

s to ₆(COO)₆sup>6−

mellitate Mellitic acid, also called graphitic acid or benzenehexacarboxylic acid, is an acid first discovered in 1799 by Martin Heinrich Klaproth in the mineral mellite (honeystone), which is the aluminium salt of the acid. It crystallizes in fine silky n ...

anions and water of crystallization. File:Mellite-asymmetric-unit-from-xtal-3D-bs-17.png, Ball-and-stick model of the

asymmetric unit In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystal, crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pat ...

of mellite File:Mellite-asymmetric-unit-from-xtal-3D-sf.png,

space-filling model In chemistry, a space-filling model, also known as a ''calotte model'', is a type of three-dimensional (3D) molecular model where the atoms are represented by spheres whose radii are proportional to the radii of the atoms and whose center-to- ...

of the asymmetric unit File:Mellite-3x3x3-unit-cells-from-xtal-3D-sf.png, Packing of 3×3×3 unit cells

References

Aluminium minerals Organic minerals Tetragonal minerals Minerals in space group 142 Luminescent minerals {{Mineral-stub

Structure

See also

References