The Altar Stone wasn't from Orkney

Fascinating update on the hunt for the source of the Stonehenge Altar Stone, and great insights into the sources of the monoliths on Orkney.

Richard E. Bevins, Nick J.G. Pearce, Stephen Hillier, Duncan Pirrie, Rob A. Ixer, Sergio Andò, Marta Barbarano, Matthew Power, Peter Turner,

Was the Stonehenge Altar Stone from Orkney? Investigating the mineralogy and geochemistry of Orcadian Old Red sandstones and Neolithic circle monuments,

Journal of Archaeological Science: Reports, Volume 58, 2024, 104738,

ISSN 2352-409X,

https://doi.org/10.1016/j.jasrep.2024.104738

(https://www.sciencedirect.com/science/article/pii/S2352409X24003663)

Abstract: Recent petrological, mineralogical and geochemical investigations of the Stonehenge Altar Stone have negated its source in the Old Red Sandstone (ORS) Anglo-Welsh Basin. Further, it has been suggested that it is time to look wider, across northern Britain and Scotland, especially in areas where geological and geochemical evidence concur, and there is evidence of Neolithic communities and their monuments. In this context the islands of Orkney, with its rich Neolithic archaeology, are an obvious area worthy of investigation. The same techniques applied to investigations of the Altar Stone and ORS sequences in southern Britain have been applied to two major Neolithic monuments on Mainland Orkney, namely the Stones of Stenness and the Ring of Brodgar. In addition, field samples of ORS lithologies from the main stratigraphic horizons on Mainland Orkney have been investigated. Portable XRF analyses of the five exposed stones at the Stones of Stenness and seven of the exposed stones at the Ring of Brodgar show a wide range of compositions, having similar compositions to field samples analysed from both the Lower and Upper Stromness Flagstone formations, with the stones at Stenness appearing to have been sourced from the Upper Stromness Flagstone Formation while the Ring of Brodgar stones possibly being sourced from both formations. Examination of the mineralogy of ORS field samples and the Stonehenge Altar Stone, using a combination of X-ray diffraction, microscopy, Raman spectroscopy and automated SEM-EDS shows there to be no match between the Orkney samples and the Altar Stone. Only two samples from Orkney showed the presence of baryte, a characteristic mineral of the Altar Stone. Another key discriminant is the presence of abundant detrital K-feldspar in all of the Orkney field samples, a mineral which has only very low abundance in the Altar Stone. In addition, the regularly interstratified dioctahedral/dioctahedral smectite mineral tosudite is present in the clay mineral assemblage of the Altar Stone, but not detected in the Orkney samples. It is concluded that the Altar Stone was not sourced from Mainland Orkney, despite considerable evidence for long-distance communications between Orkney and Stonehenge around 3000/2900 BCE.

Keywords: Altar Stone; Stonehenge; Orkney; Old Red Sandstone; Sandstone; Provenancing

Middens and Nettles

Living at All Cannings Cross with midden material scattered in the fields around me and having been involved in several excavations of the local middens I was fascinated by this discussion of growing nettles on them.

When I have been asked about the Pewsey Vale middens this is the best explanation that I can think of for them. I thought the enriched soil and the stone tools as well as the value of long nettle fibres supported it.

My theory has usually just been humoured but not taken seriously so imagine my surprise at this:

 

From: Ben Chan,

Settling the argument: The contribution of use-wear studies to understanding artefact scatters in Neolithic Britain,

Journal of Archaeological Science: Reports,  Volume 57, 2024, 104686,

ISSN 2352-409X,

https://doi.org/10.1016/j.jasrep.2024.104686.

(https://www.sciencedirect.com/science/article/pii/S2352409X24003146)

Early science and colossal stone engineering in Menga, a Neolithic dolmen (Antequera, Spain)

Abstract 

Megaliths represent the earliest form of monumental stone architecture. The earliest megalithic chambers in Europe appeared in France in the fifth millennium BCE. Menga is the oldest of the great dolmens in Iberia (approximately 3800 to 3600 BCE). Menga’s capstone #5 weighing 150 tons is the largest stone ever moved in Iberia as part of the megalithic phenomenon and one of the largest in Europe. The research presented here proposes a completely innovative interpretation of how this colossal monument was built.

https://www.science.org/doi/10.1126/sciadv.adp1295

José Antonio Lozano Rodríguez et al. ,Early science and colossal stone engineering in Menga, a Neolithic dolmen (Antequera, Spain).Sci. Adv.10,eadp1295(2024).DOI:10.1126/sciadv.adp1295

Original Position of the Altar Stone

In the recent discussions of the Altar Stone at Stonehenge variations of the equivocation that is unknown if it was originally vertical or if it was placed in its present horizontal position keep reoccurring.

Because Stone 55 fell and broke it there is assumed to be ambiguity over this. In the words of an engineering expert who has looked at the plans, the excavation records and scenarios of the collapse of the Trilithon onto it, the idea that it was a vertical stone is "knuckle-dragging, mouth-breathing stupidity that isn't worth a pitcher of warm spit". I wouldn't go so far myself just that the idea that has no logic or evidence behind it. 

It was placed as a horizontal stone. Which means that its 81 degree angle to the main Solstical Alignment is also deliberate.

As I argued in my "The Twisted Trilithon of Stonehenge" it is just one of the group of stones at the apse end of the inner horseshoe so aligned. They indicate the sunrise and sunset of the Solstical days that the main alignment indicates the other end of the day of. So the 81 Degree angle aligns to the sunrise of the Winter Solstice Sun which at the end of the day sets in line with the middle of the horseshoe. As well as the Altar stone (Stone 80), and the tallest Trilithon, there were a pair of Bluestone pillars 66 and 68 (68 has been pushed over but its original position is known from Gowland's excavation records), marked by blue circles in the plan below. There was also a pair of wooden posts to the north of the Altar Stone 3364 and 3362.

Plan based on Cleal et al

Intriguingly the layout is reminiscent of the Aberdeen recumbent stone circles -

   

Easter Aquhorthies stone circle (cropped view) by stu smith from Hampton Wick / Aberdeen, uk, CC BY-SA 2.0, via Wikimedia Commons

Dr John Hill goes even further "The Scottish Stonehenge Architect and His Aberdeenshire Stone Circles".  

The Stonehenge Palisade - a video by Paul Whitewick

Altar Stone Analyses, A Simplified Overview.

Cumulative probability density function plot of comparative Old Red Sandstone detrital zircon U–Pb datasets (concordant ages) versus the Altar Stone. Proximity between cumulative density probability lines implies similar detrital zircon age populations.

Re: A Scottish provenance for the Altar Stone of Stonehenge [2]

## Analytical Techniques

- Automated mineralogy: A TESCAN Integrated Mineral Analyser was used to study the stone's texture and mineralogy[2].

- Scanning electron microscopy (SEM): A CLARA field emission SEM provided high-resolution imaging of individual minerals like zircon, apatite, and rutile using back-scatter electron and cathodoluminescence techniques[2].

- Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS): This method was used for detailed chemical analysis of the stone[2].

## Geochronology

- U-Pb dating: This technique was applied to date zircon, apatite, and rutile mineral grains within the Altar Stone[2][4].

## Key Findings

The analysis revealed:

- The mineral grains in the Altar Stone have two distinctive date peaks at just over 1 billion years old and 458-470 million years old [5]

- The chemical composition matches rocks from the Orcadian Basin in northeastern Scotland[5][6]

- This indicates the stone originated about 435 miles (700 km) from Stonehenge[5]

The Samples

## Altar Stone Samples

- A sample labeled 2010K 240, collected from the underside of the Altar Stone in 1844[8].

- A sample labeled MS3, from an excavation near stone 1 by Colonel Hawley [7]

## Verification Methods

The researchers verified the samples through several means:

- Visual identification: Debitage fragments were initially identified based on lithological similarity to the Altar Stone[S1].

- Portable X-ray fluorescence (pXRF) analysis: This non-destructive technique was used to analyze the chemical composition of the Altar Stone's surface directly at the site[1].

- Conventional optical microscopy: Researchers examined thin sections of the stone using transmitted and reflected light microscopy[2].

- Geochemical comparison: pXRF analysis was used to compare the elemental composition of the fragments to the in situ Altar Stone[S1].

- Mineralogical analysis: Automated SEM-EDS was used to quantify the mineralogy of the Altar Stone and debitage fragments[S1].

- Petrographic analysis: Supported the identification of the debitage fragments as being derived from the Altar Stone. They also verified the authenticity of the historical sample (2010K 240) through comparison with other Altar Stone samples[8].

- The provenance of  the historical sample (2010K 240) was confirmed [22]

##  Comparative Samples of the Orcadian Basin

   - Samples were professionally collected from the Old Red Sandstone (ORS) of the Orcadian Basin in northeastern Scotland - specifically, samples came from Spittal Quarry, Caithness (sample AQ1) and Cruaday Quarry, Orkney (sample CQ1)[2].

##  Analysis Methods:

   - The samples underwent apatite U-Pb dating[2].

   - In situ thin-section analysis was used, which can help mitigate against potential contamination[2].

##  Results:

   - Apatite U-Pb age components from these Orcadian Basin samples matched those from the Altar Stone[2].

   - Group 1 apatite from Cruaday (CQ1) yielded an age of 473 ± 25 Ma.

   - Group 1 apatite from Spittal (AQ1) yielded an age of 466 ± 6 Ma.

   - Group 2 apatite from Spittal (AQ1) yielded an age of 1,013 ± 35 Ma.

   - Apatite U-Pb dating of MS3 (Altar Stone Sample) yielded 117 analyses.

   - Two distinct groups of apatite were identified:

     Group 1:

     - 108 analyses

     - Lower intercept age: 462 ± 4 Ma (MSWD = 2.4)

     - Upper intercept 207Pb/206Pb: 0.8603 ± 0.0033

     Group 2:

     - 9 analyses

     - Lower intercept age: 1,018 ± 24 Ma (MSWD = 1.4)

     - Upper intercept 207Pb/206Pb: 0.8910 ± 0.0251

 - Apatite Lu–Hf data for the Altar Stone. A) Apatite Lu–Hf isotopic data and ages for thin-section 2010K.240. B) Apatite Lu–Hf data for secondary references. See Spreadsheet in Citation [20]

-   - The Early Palaeozoic apatite components from Caithness and Orkney (473 ± 25 Ma and 466 ± 6 Ma) are identical, within uncertainty, to the Altar Stone Group 1 apatite (462 ± 4 Ma)[2].

-Zircon age data was collated with with the U–Pb analyses1 of "FN593" (another fragment of the Altar Stone) . (This should be FN573 [23] - SH08 Context 16 FN573 (previously erroneously labelled as FN593). From a Roman context at Stonehenge. Described in Ixer and Bevins (2013) under FN593.[24])

The result was at >95% certainty, no distinction in provenance can be made between the Altar Stone zircon age dataset (n = 56) and those from the Orcadian Basin (n = 212), Svalbard ORS (n = 619) and the Laurentian basement.

- Rutile U–Pb Results: From Altar Stone sample MS3 two groups were obtained. "Group 1 which constitutes 83 U–Pb rutile analyses, forming a well-defined mixing array on a Tera-Wasserburg plot between common and radiogenic Pb components. This array yields an upper intercept of 207 Pb/ 206 Pb i = 0.8563 ± 0.0014. The lower intercept implies an age of 451 ± 8 Ma implies an age of 451 ± 8 Ma

Group 2 comprises 9 grains, with 207 Pb corrected 238 U/206 Pb ages ranging from 591–1,724 Ma. Three grains from Group 2 define an age peak 68 at 1,607 Ma. Given the spread in U–Pb ages, we interpret these Proterozoic grains to represent detrital rutile derived from various sources."

##  Significance:

   - These matches support a provenance from the Orcadian Basin for the Altar Stone[2].

##Citations:

[1] https://pure.aber.ac.uk/ws/portalfiles/portal/50647128/linking_derived_debitage_to_the_stonehenge_altar_stone_using_portable_x_ray_fluorescence_analysis.pdf

[2] https://www.nature.com/articles/s41586-024-07652-1

[3] https://www.sciencealert.com/stonehenge-mystery-scientists-reveal-how-they-traced-the-altar-stone

[4] https://www.cnn.com/2024/08/14/science/stonehenge-altar-stone-scotland/index.html

[5] https://www.somersetlive.co.uk/news/history/stonehenge-altar-stone-stunning-twist-9485735

[6] https://www.cbsnews.com/news/stonehenge-altar-stone-came-from-scotland-not-wales-research/

[7] https://www.cambridge.org/core/journals/mineralogical-magazine/article/linking-derived-debitage-to-the-stonehenge-altar-stone-using-portable-xray-fluorescence-analysis/23E9A00C0C2B9FAC0BC74AC11AAE5B2D

[8] https://pure.aber.ac.uk/ws/portalfiles/portal/65608443/Assessing_the_authenticity_of_a_sample_taken_from_the_Altar_Stone_accepted_version_v2_Archaeologican_Science.pdf

[9] https://www.sciencedirect.com/science/article/abs/pii/S2352409X23001487

[10] https://phys.org/news/2024-08-stonehenge-giant-altar-stone-northeast.html

[11] https://www.cnn.com/2024/08/14/science/stonehenge-altar-stone-scotland/index.html

[12] https://www.academia.edu/81723766/Handheld_X_Ray_Fluorescence_Analysis_HH_XRF_a_non_destructive_tool_for_distinguishing_sandstones_in_historic_structures?uc-sb-sw=19875163

[13] https://www.snexplores.org/article/stonehenge-altar-stone-origin-chemistry-minerals

[14] https://www.nature.com/articles/s41586-024-07652-1

[15] https://data.jncc.gov.uk/data/d156c160-558d-4855-9927-6066e183045e/gcr-v31-old-red-sandstone-c2.pdf

[16] https://en.wikipedia.org/wiki/Orcadian_Basin

[17] https://nora.nerc.ac.uk/id/eprint/516767/1/CR16017.pdf

[18] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9230696/

[19] https://www.sciencedirect.com/science/article/pii/S0191814123001396

[20] https://pure.aber.ac.uk/ws/portalfiles/portal/65608443/Assessing_the_authenticity_of_a_sample_taken_from_the_Altar_Stone_accepted_version_v2_Archaeologican_Science.pdf

[21] https://static-content.springer.com/esm/art%3A10.1038%2Fs41586-024-07652-1/MediaObjects/41586_2024_7652_MOESM4_ESM.xlsx

[22] https://www.sarsen.org/2022/09/the-altar-stone-sample-provenance.html

[23] https://research.aber.ac.uk/files/38490241/Altar_Stone_Final_submitted_v6_4_June_1_1_.pdf

[24] https://www.academia.edu/5464937/Chips_off_the_old_block_The_debitage_Dilemma

(Lightly edited from originals kindly supplied - extra citations retained for further research) 

The Source of the Altar Stone Fragment

As part of the 1958 excavation of Altar Stone, Stone 80, a series of photographs were taken of the exposed stone. 

Only one of them is publicly available from the Historic England archive, and whilst it isn't the clearest of the series, it does show the break in the stone clearly. 

And the space where Captain Richard Beamish removed the sample that is now in Salisbury Museum and is the fundamental in the recent analysis of the stone. 

The size and shape is correct and a similar loose fragment is still there. Without excavation and refitting it, which will never be allowed, I can't be 100% certain, but it does prove that the Altar Stone is the physical as well as the geochemical match to the sample.