Hubbry Logo
AbelsoniteAbelsoniteMain
Open search
Abelsonite
Community hub
Abelsonite
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Abelsonite
Abelsonite
Abelsonite
View on Wikipedia
from Wikipedia
Abelsonite
Abelsonite from the Green River Formation, Uintah County, Utah, US
General
CategoryOrganic minerals
FormulaC31H32N4Ni[1]
IMA symbolAbl[2]
Strunz classification10.CA.20
Dana classification50.4.9.1
Crystal systemTriclinic
Space groupP1 (No. 2)[3]
Unit cella = 8.508, b = 11.185 Å
c = 7.299 [Å], α = 90.85°
β = 114.1°, γ = 79.99°
Z = 1[1]
Identification
ColorPink-purple, dark greyish purple, pale purplish red, reddish brown
CleavageProbable on {111}[1]
FractureFragile[4]
Mohs scale hardness2–3
LusterAdamantine, sub-metallic
StreakPink
DiaphaneitySemitransparent[1]
Specific gravity1.45
Optical propertiesBiaxial[1]
Ultraviolet fluorescenceNon-fluorescent[4]
Absorption spectraStrong reddish brown to reddish black[1]
References[5]

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.

Description

[edit]

Abelsonite is semitransparent and pink-purple, dark greyish purple, pale purplish red, or reddish brown in color.[1][5] The mineral occurs as thin laths or plates or small aggregates up to 1 cm (0.39 in).[1] The mineral is soluble in benzene and acetone and is insoluble in water, dilute hydrochloric acid, and dilute nitric acid.[6]

Occurrence and formation

[edit]

The mineral is known only from the Parachute Creek Member of the Green River Formation.[7] It has been known from the Uinta Basin in Utah since its discovery and from the Piceance Basin in Colorado since 1985.[7] Abelsonite occurs in association with albite, analcime, dolomite, mica, orthoclase, pyrite, and quartz.[1]

Abelsonite is a secondary mineral that formed in fractures, vugs, and bedding planes of oil shale.[1][7] The mineral probably formed from diagenesis of chlorophyll, likely chlorophyll a, which was transported as an aqueous solution into a favorable geologic setting. [7][8] Alternative source are Methanogen Archea, where close compound is used in Cofactor F430 critical for methane production.

In 2003, abelsonite was fully synthesized for the first time.[9]

Structure

[edit]
Structure of abelsonite

In 1989, abelsonite was the only known geoporphyrin to have a crystalline structure.[7][a] Most geoporphyrins occur as a series of homologues spanning a large range of carbon numbers.[7] The porphyrin which comprises abelsonite is common, but it does not usually occur in isolation from other porphyrins.[10]

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.[11] The mineral crystallizes in the triclinic crystal system.[1]

History

[edit]

The mineral was first noted in 1969 in a core sample made by the Western Oil Shale Corporation in Uintah County, Utah.[12] It was described in 1975 in the journal Geological Society of America Abstracts with Programs.[13] The mineral was named after Philip H. Abelson (1913–2004), a long-time editor of the journal Science,[7] for his work in organic geochemistry.[14]

Type specimens are held in The Natural History Museum in London and the National Museum of Natural History in Washington, D.C.[1]

See also

[edit]

Notes

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Abelsonite

View on Grokipedia
from Grokipedia
Abelsonite is a rare classified as a with the Ni(C₃₁H₃₂N₄), representing the only known organonickel mineral species. It forms as a secondary product through the of in ancient sedimentary environments, serving as a chemofossil that offers valuable insights into organic geochemistry and the preservation of biological molecules in geological records. First identified in 1969 within drill cores from the Mahogany Zone of the Green River Formation in , USA, abelsonite was formally described as a new in 1978 by Charles Milton and colleagues, with approval by the International Mineralogical Association (IMA) in 1975. The mineral is named in honor of Philip H. Abelson, a pioneering geochemist and then-president of the Carnegie Institution of Washington, recognizing his contributions to understanding organic compounds in geological contexts. Its type locality is the oil shale beds of the Eocene-age Green River Formation, where it occurs in association with minerals such as , , , dolomite, , and K-Fe micaceous phases. Abelsonite crystallizes in the triclinic system with P1 and parameters a = 8.442 , b = 10.892 , c = 7.275 , α = 90.47°, β = 113.16°, γ = 78.08°, and a calculated of 1.44 g/cm³. It appears as aggregates of platy crystals up to 3 mm long, exhibiting colors from pink-purple to dark reddish-brown in hand specimen and red or reddish-brown in transmitted light, with a semimetallic to adamantine luster and translucent diaphaneity. The mineral has a hardness below 3 on the , probable cleavage on {111}, and a fragile ; its is based on deoxophylloerythroetioporphyrin, a derivative of lacking the characteristic isocyclic ring.

Physical and Chemical Properties

Appearance and Physical Characteristics

Abelsonite occurs as aggregates of platy , typically forming thin laths or plates up to 3 mm in length, sometimes reaching patches over 2 mm in diameter. These aggregates exhibit a fragile structure, making the mineral delicate and easily damaged during handling. The mineral displays a range of color variations, including pink-purple, dark reddish-brown, pale purplish red, and dark grayish purple, which contribute to its distinctive appearance as a . Its luster is submetallic to adamantine, providing a somewhat shiny yet subdued sheen. Abelsonite is semitransparent to translucent, allowing partial light transmission that highlights its organic-derived hues. The density of abelsonite is calculated at 1.45 g/cm³, with measured values ranging from 1.33 to 1.48 g/cm³, reflecting its lightweight, organic composition. Hardness is less than 3 on the , consistent with its soft, brittle nature.

Chemical Composition and Formula

Abelsonite is an with the C31H32N4NiC_{31}H_{32}N_4Ni, where a is complexed within a . This formula represents a deoxophylloerythroetioporphyrin , making abelsonite the only known naturally occurring organonickel mineral. The in abelsonite exists as the Ni²⁺ cation, centrally coordinated in a square-planar arrangement within the ring, which consists of four units linked by methine bridges and featuring ethyl and side chains characteristic of the deoxophylloerythroetioporphyrin structure. This coordination imparts stability to the complex, distinguishing it from typical inorganic minerals. Abelsonite holds International Mineralogical Association (IMA) approval status as a valid species, designated IMA1975-013, based on its unique composition and natural occurrence. Elemental analysis of the type specimen from the Green River Formation confirms the proportions of its constituent elements, with microprobe measurements yielding approximately 11–14 wt% Ni and 40–50 wt% C, while N was below detection limits around 10 wt% due to the volatility of organic components during analysis. Theoretical calculations for the ideal formula predict 71.70 wt% C, 6.21 wt% H, 10.79 wt% N, and 11.30 wt% Ni, validating the proposed .

Geological Occurrence and Formation

Discovery Sites and Localities

Abelsonite was first identified in the Green River Formation, , USA, which serves as its type locality. This mineral occurs specifically within drill cores from the Mahogany Zone of the formation. Beyond the type locality, abelsonite has been documented in a total of eight drill cores located in or near the , . These occurrences are confined to the region, with no confirmed reports from other global sites. The mineral appears as aggregates of platy crystals on fracture surfaces within the host rock. Abelsonite is associated with organic-rich , where it forms thin encrustations or coatings up to several millimeters in size. Common accompanying minerals in these settings include , , , dolomite, , and a potassium-iron micaceous phase. It was identified in 1969 during studies of petroleum geochemistry in the Green River Formation's . This mineral derives from the diagenetic alteration of , though detailed processes are examined elsewhere.

Formation Processes

Abelsonite forms as a secondary mineral through the diagenetic alteration of organic matter in oil shale deposits, primarily via the conversion of chlorophyll derivatives into nickel porphyrins. This process begins with the degradation of chlorophyll molecules, such as chlorophyll a, present in the remains of ancient aquatic organisms within lacustrine sediments. During early diagenesis, these porphyrin precursors undergo demetallation and structural modifications, including the loss of functional groups like the propionic acid side chain, leading to the formation of deoxophylloerythroetioporphyrin. Nickel ions, available from the surrounding sedimentary environment, then complex with the porphyrin ring to yield the stable Ni(C31H32N4) structure of abelsonite. The formation occurs under low-temperature, anoxic conditions typical of buried organic-rich sediments, where maturation of and hydrocarbons proceeds without significant oxidative degradation. In these reducing environments, found in Eocene lacustrine oil shales like those of the Green River Formation, the precursors are transported via aqueous solutions into fractures, vugs, and bedding planes of the host rock. This migration allows for precipitation in lithologically favorable sites, such as those enriched in , where the pH and metal ion concentrations support porphyrin metallation. The process is facilitated by the unique of ancient lake systems, such as Lake Uinta, which provided the necessary anoxic bottom waters and organic influx to concentrate these compounds. Abelsonite's persistence as a chemofossil stems from its crystalline and , which resist further diagenetic breakdown even under prolonged burial. Unlike more labile organic compounds, the nickel-complexed exhibits low in common solvents and remains intact amid ongoing generation, serving as a marker of early sedimentary organic . This durability highlights its role in preserving biochemical signatures from prehistoric ecosystems in hydrocarbon-rich settings.

Crystal Structure and Analysis

Structural Description

Abelsonite crystallizes in the with P1ˉP \bar{1}. The unit cell parameters, determined from single-crystal X-ray diffraction data collected at 100 K, are a=8.4416(5)a = 8.4416(5) , b=10.8919(7)b = 10.8919(7) , c=7.2749(4)c = 7.2749(4) , α=90.465(2)∘\alpha = 90.465(2)^\circ, β=113.158(2)∘\beta = 113.158(2)^\circ, γ=78.080(2)∘\gamma = 78.080(2)^\circ, and a volume of 599.74(6)599.74(6) ³, with one per (Z=1Z = 1). The atomic arrangement features nearly planar porphyrin molecules, each consisting of a 20-membered tetrapyrrole macrocycle centered on a Ni²⁺ ion, stacked approximately parallel to the (1̅11) plane and held together by weak van der Waals forces. These molecules adopt a deoxophylloerythroetioporphyrin configuration, characterized by five methyl groups at positions 2, 3, 7, 12, and 18, ethyl groups at positions 8 and 17, and an ethyl group bridging positions 13 and 15, forming the etio-type side chain pattern typical of geoporphyrins. Within each molecule, the nickel ion is covalently bonded to four nitrogen atoms of the pyrrole rings via coordination bonds, with Ni–N distances of 1.92 Å and 1.97 Å, resulting in a slightly ruffled macrocycle. Intermolecular interactions cause the stacked layers to be staggered, with adjacent molecules tilted relative to one another to accommodate the side chains. No twinning has been reported in abelsonite crystals, which occur as small aggregates of thin plates or laths up to 1 cm in size. However, the structure exhibits orientational disorder, where each porphyrin molecule occupies two possible orientations randomly within the lattice, contributing to the overall P1ˉP \bar{1} symmetry.

Analytical Methods and Data

The characterization of abelsonite employs several analytical techniques to elucidate its crystal structure and molecular composition, with a focus on its unique status as an organic nickel porphyrin mineral. Single-crystal X-ray diffraction (XRD) serves as the primary method for structural determination, utilizing type specimens from the Green River Formation in Utah, USA, housed at the Geophysical Laboratory of the Carnegie Institution of Washington. These analyses confirm a triclinic crystal system with space group P1ˉP \bar{1} and unit cell parameters a = 8.508(24) Å, b = 11.185(27) Å, c = 7.299(15) Å, α = 90°51'(15), β = 114°08'(12), γ = 79°59'(13), and Z = 1, based on data collected with Mo Kα radiation from the original 1978 description. Infrared (IR) spectroscopy complements XRD by identifying key functional groups, particularly those associated with the porphyrin ring and metal coordination. Characteristic IR absorption bands include 2970, 2915, and 2860 cm⁻¹ attributed to C-H vibrations, alongside weaker bands at 620, 602, 535, 512, and 441 cm⁻¹ that indicate C-N stretches and Ni-N bonding interactions within the metalloporphyrin framework. These spectral features, obtained from thin-film or samples, align with the deoxophylloerythroetioporphyrin structure derived from degradation. Raman spectroscopy provides insights into vibrational modes, revealing shifts consistent with the D_{4h} symmetry of the porphyrin macrocycle, including skeletal stretching modes around 1300–1600 cm⁻¹ and metal-nitrogen deformations below 300 cm⁻¹. Spectra from unoriented samples, excited at 532 nm, display a complex profile due to the molecular stacking, with data archived in the RRUFF database for reference. Electron microprobe analysis supports these findings by quantifying elemental composition, yielding approximately 11–14 wt% Ni and confirming the empirical formula NiC_{31}H_{32}N_4 through stoichiometric estimation of C, H, and N. The organic composition necessitates specialized handling protocols, such as inert atmospheres and low-temperature measurements, to mitigate thermal decomposition and oxidative instability during analysis.

History and Significance

Discovery and Naming

Abelsonite was initially observed in 1969 by Lawrence B. Trudell during core logging for deposits in the Green River Formation, Uintah County, Utah. This finding emerged from broader research on the geochemical properties of organic-rich sedimentary rocks, where unusual crystalline material was noted on fracture surfaces within drill cores from the Mahogany Zone. The mineral was formally described as a new species in 1978 by Charles Milton, Edward J. Dwornik, Patricia A. Estep-Barnes, Robert B. Finkelman, Adolf Pabst, and Susan Palmer in a paper published in the American Mineralogist, based on detailed analyses of samples from multiple drill sites. Earlier observations, including initial identification around 1970 by L. B. Trudell, contributed to the characterization process leading to this publication. Abelsonite received official approval from the International Mineralogical Association (IMA) in 1975 as a valid new species. The name honors Philip Hauge Abelson (1913–2004), an American and geochemist renowned for his foundational work on the stability and geochemical cycling of organic compounds in ancient fossils and sediments, including pioneering studies on preserved in geological materials.

Geochemical and Biological Importance

Abelsonite serves as a chemofossil, representing a direct diagenetic derivative of chlorophyll a, which underscores its origins in photosynthetic biological processes within the anoxic Eocene lake sediments of the Green River Formation. This nickel porphyrin mineral forms through the transformation of , where the central magnesium ion is replaced by , preserving the core ring structure amid degradation. Its presence in specific stratigraphic zones, such as the Mahogany Zone, highlights the role of localized reducing environments that facilitated the survival of this biologically derived compound over millions of years. Geochemically, abelsonite acts as an indicator of nickel availability and the diagenetic pathways of porphyrins in petroleum source rocks, particularly in oil shales like those of the Parachute Creek Member. The mineral's crystallization in fractures and vugs reflects selective metal-organic complexation under conditions of moderate nickel concentrations and low oxygen, influencing the maturation of kerogen into hydrocarbons. As the only known crystalline geoporphyrin, it provides insights into the stability of metal-porphyrin complexes during sediment diagenesis, serving as a proxy for paleoredox conditions and trace metal cycling in ancient lacustrine systems. In 2017, the complete crystal structure of abelsonite was determined using single-crystal X-ray diffraction, confirming its triclinic symmetry and providing further insights into the stability of geoporphyrins. From a biological perspective, abelsonite exemplifies early organic mineralization, demonstrating how metal-organic frameworks can endure geological timescales as rare examples of preserved biomolecules. Its derivation from offers evidence of photosynthetic ecosystems in Eocene paleoenvironments, where promoted the transition from labile to stable mineral phases. In research applications, abelsonite informs studies on formation by elucidating roles in source rock and hydrocarbon generation processes. It also aids reconstructions of paleoenvironments, revealing details of ancient lake chemistry and organic preservation in the . Furthermore, as a unambiguous biological , abelsonite holds potential in for identifying life signatures on other planets through the detection of preserved metal-porphyrin complexes.
Add your contribution
Related Hubs
User Avatar
No comments yet.