Abelsonite

What is Abelsonite?

Abelsonite is a nickel porphyrin mineral with chemical formula C31H32N4Ni. It was discovered in 1969 in the U.S. State of Utah and described in 1975. The mineral is named after geochemist Philip H. Abelson. It is the only known crystalline geoporphyrin. The crystals are soft, with a Mohs scale rating is 2 to 3. 

It has a low specific gravity of 1.45. Removal of the nickel by treatment with methanesulfonic acid permitted confirmation of the structure on the free base porphyrin and demonstrated structural integrity under the conditions required for demetallation. The structure is best accounted for geochemically by the hypothesis that Abelsonite is derived from a chlorophyll.

Abelsonite description and its diagnostic

Abelsonite is semitransparent and pink-purple, dark greyish purple, pale purplish red, or reddish brown in color. The mineral occurs as thin laths or plates or small aggregates up to 1 cm. The mineral is soluble in benzene and acetone and is insoluble in water, dilute hydrochloric acid, and dilute nitric acid. 

Associated authigenic minerals include orthoclase, pyrite, quartz, dolomite, analcime, and a K--Fe micaceous mineral. Abelsonite occurs as aggregates of platy crystals, as much as 3 mm long, that range in color from pink-purple to dark reddish-brown. As of 1989, Abelsonite was the only the known geoporphyrin to have a crystalline structure. 

Most geoporphyrins occur as a series of homologues spanning a large range of carbon numbers. The porphyrin which comprises Abelsonite is common, but it does not usually occur in isolation from other porphyrins. The mineral is a deoxophylloerythroetioporphyrin (DPEP), with nickel occupying the center of the porphyrin ring. 

Most of the mineral consists of a C31 porphyrin with small quantities of a C30 norisomer. The mineral crystallizes in the triclinic crystal system.

Associated authigenic #minerals include orthoclase, pyrite, quartz, dolomite, analcime, and a K--Fe micaceous mineral. As of 1989, #abelsonite was the only the known geoporphyrin to have a crystalline structure.https://t.co/q64nCc2WtT

— Sattar Yekta (@anbar_asia) June 13, 2021

Abelsonite Occurrence and formation

The mineral is known only from the Parachute Creek Member of the Green River Formation. It has been known from the Uinta Basin in Utah since its discovery and from the Piceance Basin in Colorado since 1985. Abelsonite occurs in association with albite, analcime, dolomite, mica, orthoclase, pyrite, and quartz. s. 

All the samples were found in or nearthe Mahogany Zone, probably in the lower part. The Mahogany Zone is the subsurface equivalent of the kerogen-rich Mahogany Ledge in the Parachute Creek member of the Green River Formation. Pink platy Abelsonite was found in one sample. Abelsonite is a secondary mineral that formed in fractures, vugs, and bedding planes of oil shale. 

The mineral probably formed from diagenesis of chlorophyll, likely chlorophyll a, which was transported as an aqueous solution into a favorable geologic setting. In 2003, Abelsonite was fully synthesized for the first time.

Abelsonite history

The mineral was first noted in 1969 in a core sample made by the Western Oil Shale Corporation in Uintah County, Utah. It was described in 1975 in the journal Geological Society of America Abstracts with Programs. The mineral was named after Philip H. Abelson a long-time editor of the journal Science for his work in organic geochemistry. 

Chemically a nickel porphyrine derivative, classified as deoxophylloerythroetioporphyrin. Unique combination of elements; the only organonickel mineral known. Formed at depth. Abelsonite is accompanied by its structural norisomer; the surrounding shale contains other Ni porphyrins, which represent a series of more extended homologues. 

methyl groups in the 2, 3, 7, 12, and 18 positions, ethyl group in the 8 and 17 positions. According to Milton et al. the molecules in Abelsonite are not planar. The substitution pattern in the mineral is genetically related to a typical chlorophyll. The potential precursor to Abelsonite is 17 desethyl, 17 propionic acid. 

Worth of notice is an unnamed mineral coded as 'UM1984-14-CH:ClNOV', which is a natural vanadyl deoxophylloerythroetioporphyrin, the second known metalloporphyrin mineral, although not isostructural with abelsonite. There are also coal seams, oil-shales, and mineral deposits of economic significance; and of course famous fossil beds of Fossil Lake containing incredibly preserved fossil fish.