2011-12-09

Patina on artefacts

Patina on artifacts , some remarks on the subject


 Image above left: A flake  from Rijckholt (Ryckholt flint mine, The Netherlands)  with a white patina,  at right, a cross section of the same flake, showing the very thin patina layer at the arrow;  the inside of the flake is the original, fresh more dark colored color.


 Another example of changing colors and changing appearence by the patina effect. The flint in the right picture looks dull grey colored and is showing iron stains ( reddish brown), but when we break the flint, it appears to be a black type Rijckholt flint, with white dots, invisible at the surface ( right).

Patina, ( Dutch) problems in the definition?
The discussion about  patina on artifacts is not new. For this, I can point at  the website of the APAN (APANarcheo) and the excellent PDF file about 'hyaliet" by G.J. van Noort ( Dialezing over Hyaliet of windlak PPT) (1) . Here, the points of view are very wide ( discussions on the "steentijdforum" ( members only, [ discussion between M. Niekus vs. K. Geertsma] ) with on the one side people defending the patina as originating from glacial ( surface) influences,( Niekus, Vermeersch) and on the other hand people defending the view it's a geological ( soil-) process where the ( environmental, climate depending ) soil -circumstances are the main factor to produce patina on the flint's surface ( Hurst & Kelly 1961) (2), Mousser et al. 2007, Van Noort 2010).
A brief tour around the opinions
Howard claims in his article about river ( caused) -patina on flint artifacts ( 1999), that the white patina on artifacts is not the same as gloss patination which is caused by surface alteration (3.). Craddock  mentions the formation of white patina in alkaline soils, contrary to iron oxidation in acid sands/ gravels.( Craddock 2009)(4).  In 1900 , S. Hazzledine Warren describes a patinated flint implement from the palaeolithic, related to chalk rich -layers (Palaeolithic flint implements from the Chalk Downs of the Isle of Wight and the Valleys of the Rivers Western Yar and Stou, abstract of Cambridge Journals online )
Rottländer (5), who has investigated the chemistry influences by experiments, in his article mentions the mainly influence of soil conditions :…Rottländer suggests an alkalinity of pH > 10 for white patina to develop and an acidity of pH = 3.5-4.0 for gloss patina formation… ; (cit)  As to its origin, most authors agree that alkaline environments induce white patina; Rottlander (1975a) mentions a pH of 10.0 or higher. Both Schmalz (1960) and Plisson (1985a) have experimented with various alkaline solutions and were able to reproduce white or bluish patina in a relatively short time …" (cit)  …Toconclude, it would appear that white patination can occur under different circumstances. First of all, it develops in alkaline environments,…(end cit.)
In the article of Van Noort (G.J. van Noort, 'Moganiet', een poreuze witte patina rond vuursteen, APAN Extern 14/ 2010 pp. 99 -100)(6) we can read about the mineralogist's view, claiming the white patina to be a porous shell around an artifact, consisting of "moganite", filling up the artifacts' surface holes, also related to certain soil -environments. Van Noort also mentions in his article the origin of the brownish - yellow patina color as 'infiltration of iron in the outer crust…. the white moganite has changed in a brown- yellow color". So in his conclusions Van Noort defines the white patina as the mineral  'moganite.'
Last but not least we observe the practical examination on producing patina on artefacts:
…"Where the flints had lain in a chalk-alkaline soil they developed a milky white or brown patina,and it was discovered that boiling the flint in strong caustic soda solution rapidly gave the desired effect(290) . A brown patina was produced by the addition of some rusty nails to the caustic soda solution." (Mark Jones, British Museum, in:Fake? The art of deception, Jones(ed.) University of California Press ( with : Craddock/Barker) 1990

My own observations on this subject
In the region of South- Limburg (NL) / Voeren (B) and Walloon (B), artifacts from the M -Palaeolithic period could be patinated, but often the artifacts are remarkable fresh ( though some weathering is visible).
In stead of a heavy brownish or white cream patina we often notice a dull artefact- surface.  I think, at least for this region , ( in the typical condition of loess/ undrained soils)  there's a relation with the minerals ( i.c. the amount of chalk) in the environmental location of the artifact. When artifacts are connected to the (Middle- Late) Pleistocene gravel-beds of the former river terraces, the artifacts mostly are unpatinated, and look remarkable 'fresh'. Of course this is not only the case with artifacts from the gravel-bed, all other stones from the same gravel-layers have the same certain 'freshness'.
Typical Levallois points, that must have a pre- Aurignacien date , so MP, often look very 'fresh', when they are found at the surface.
This surface however, was originally covered by a thick- sometimes even up to 20 m thick - loess- cover in the last ten- thousands of years. Only at the beginning of the Bronze age- and later periods like the Roman periods the land was cleared and used for cultivation. The real erosional processes on the slopes only are starting in the Bronze ages. Former erosion, like during the Weichselian and early late Glacial period was not always big, the worst form is the thawing of the permafrost after rapid cold periods, when no bush vegetation was there to protect the soil for erosion. Here we distinguish the pseudogley- soil in the soil profile of peri-glacial periods.
However, on the same locations we also find heavily white ( sometimes also white-yellow, brown or blue)  patinated artifacts that have been embedded in chalk rich layers (like loess) and are now found on the surface.
I think there's a relation between the patina and minerals in the soil, especially between iron rich / poor layers and chalk rich/ poor horizons  from the loess/ lime bedrock. Indeed, we find 'fresh ' Levallois flakes, covered with traces of oxidated iron (rust). Oxidation of iron is well known on impermeable soils, where  iron banks are naturally formed in case of e.g. creek swamps. In the loess layers we find these impermeable layers in the form of loam-/ clay  layers (Dutch:  kleefaarde). I think artifacts that were located close to these layers in the thousands of years after deposit, will remain relative fresh, because of the iron in the particular soil layer. On the other hand, artifacts covered in (upper, leached ) loess layers  have a strong influence from the chalk (Ca). This chalk could form new compounds on the artefact's surface. This is , of coarse depending on the flint- type,where I notice important differences between e.g. the coarse Hesbaye - type flint ( like the grey coarse Lanaye- Pietersberg 1 and Pietersberg2), that mostly do not show any patinas, and Ryckholt -type flint, more fine grained, more clear, showing patina patterns in white and blue - patina that is even dating from the Neolithic .

Fluvial -type flint, showing heavy patina, a chemical reaction of the surface with minerals of the environment. dorsal view

The same artifact, ventral view, obviously recently broken, showing the fresh inside

Why is patina so important?

When I started collecting, I was told by official archaeologist's in Holland, a Middle- Palaeolithic artifact always is covered with a heavy patina. Let's say, the more the better. If the patina is absent, it's definitely a Neolithic artifact. On the other hand, artifacts from the Rijckholt Mining Complex - region with a Neolithic date could very well be patinated. They didn't tell me why. So patina would be a parameter to define the age of the artifact. And, even more, patina would be the evidence against falsifications, not only argued by opponents of the so called "Vermaning- artifacts", but also by flint -stone tools sellers who claim the authenticity of an artifact depends on the artefact's' patination.
When you visit the Mining Complex at Rijckholt, you'll find lots of (partially) patinated artifacts, but also non-patinated. And even "semi patinated" pieces ,: only one side or a very small part of the artefact  is covered with a blue- white patina, the other side is absolutely fresh. Why could patina be such a reliable parameter for defining the period when patina appears to be so different on the artifacts?(***)
White patina on a traditional miners pick from the Neolithic Ryckholt Mine Complex. Is patina so reliable for appointing an artifact to a certain  period? This patina however is not the same as we find on Acheulean type artifacts, but tells us more about the percentages of chalk in the soil.
There's  – to my opinion -one possible explanation: patina is caused by the direct ( primary or  secondary doesn't matter) context of an artifact after deposit, causing a chemical reaction. Taphonomic processes caused by certain minerals will cause a certain patina on the artifacts, depending on the type of silex, sustainability, permeability of the surface, pollution of the silex type etc.
There's  also a theory about  the whether (wind  /sun)  causing the patina on artifacts, like dehydrating  the artifact.
Where does the patina layer come from? You would expect the wind/ sand/ soil would erase parts of the stone's surface. When you write with the wrong pencil on an artifact, you see the ink spreads in the layer. This supports the ideas of Van Noort, about a porous layer, called after the mineral moganite.
So the process was still ongoing when collecting the artifact. When the glacial winds/ sun caused this patina, this process would have stopped. On the other hand: is patina an unidirectional process? Could an artifact become unpatinated after?

Patina caused by ( special) use of the artifact
The best known use patina is the shiny layer on the working edge caused by the influence from plants ( such as by cutting the corn-stems, hammering nuts etc.) This patina is only visible on the sharp working edge of the tool.
Another possible patina is a shiny patina, maybe caused by the use of the artifact in combination with grease. In this case only parts of the tools are patinated.This patina is in most cases shiny, but sometimes it could be dull as well, probably depending on the type of flint.

Iron staining on artefacts
Hurst and Kelly describe the two possible major changes at the flint artifacts, as a contrast between an alkaline environment (  showing white patina on the artifact) and an environment rich in iron ( e.g. iron oxide and hydrous iron oxide). The latter will cause  either brownish stains on the artifact, or a brown patina. Sometimes we find white patinated artifacts, with brown stains on it, mainly on the 'ribs'. This is usually not caused by the plough, but this marks a change in position in the artifacts position in the soil layers. The main cause is of coarse the impurity of the flint itself. The authors came to the conclusion, we cannot date the artifacts by only the patina, because environmental circumstances change a lot during the thousands of years.
Iron stains at the surface of an artifact
Is (white) patina on the artifact required  to place it into the Palaeolithic period?
I don't believe so. Referring to other taphonomic processes, e.g. on seeds or iron objects, we distinguish a whole range of possible changes in/on the artifact, depending on environmental factors in the artefact's context in the soil during the centuries ( or thousands of years). These factors could be e.g. the acidity, the amount of certain minerals, the characteristics of the artifact itself. Not all flint type will respond to these environmental factors in the same way. This is also argued in Van Noorts article (APAN Extern 14), different flint types respond different at e.g. becoming a crust with patina. So patina could be a true helpful indication for artifacts about the original period it dates from. On the other hand, unpatinated artifacts could as well be very old ( Palaeolithic) , depending on the type of soil and the specific location in the stratigraphy where they remain over a  very long period. Most of the time however we find patinated objects from the oldest periods, see e.g. the Halbkeil van Zuid Limburg, found by Jan Willem van der Drift,  where a white moganite patina exists, together with a diffuse patina, that has weathered over long time.

Image above: left burned piece of flint, middle patinated artifact with red stains and craquelé of the surface; right: the appearence of patina on a Ryckholt artifact, a spotted, light, dull patina.

Intense patina on a quartz, possibly  used for cutting vegetable material (?)

Hafting material?
Sometimes remains from hafting ( by lime tree, resin) are still  visible on an artifact (7).

Resin traces on a possible neolithic core

Natural patina appearing on a quartz. In studying the patinas on  quartz cobbles, I strongly have the idea this is a logical step in the crystallization of the quartz, where mineralization from the environment influences the growth of crystals in/ on the quartz

Different patinas on a single piece of flint. The brown patina is altered by white garlands of white patina, following the chemical characteristics of the flint
Patina on quartzite pebble tools. The impact point is visible on the  left artifact ( bottom right). The patina on quartzite ( flakes, cores) can appear in different stages: in the first stages we distinguish only  scattered shiny particles at the  flake blow's  surface, in the later stages the patinas are more intensified, showing a complete bright surface. Artifact left has a small unpatinated part in the middle, caused by recent damage.

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Notes / references

APAN archeo  ( Van hyaliet tot vers, G.v. Noort)
(1) G.J. van Noort,
2010 APAN Extern 14, , "Moganiet", een poreuze witte atina rond vuursteen  ( pp.99-100)
(2) Vernon J. Hurst & A.R. Kelly, 1961, in:  Patination of Cultural Flints Flint artifacts can be dated by cortical changes in mineralogy and texture - free abstract
H. Mousser, A. Madani, R. Amri, A. Mousser and A. Darchen;  2007  Contribution of micro-chemical surface analysis of archaeological artifacts
(3) Cit. Clavin Howard, 2002 gloss patina
Howard, 1999 River patina on flint artifacts: Features and genesis; in Plains anthropologist
Pierre M. Vermeersch(ed.), Palaeolithic quarrying sites in Upper and Middle Egypt K.U. Leuven,  2002pp 37 a.s.:
"…The artefacts from the Middle Layer are characterized by a white patina. In areas where the Upper Layer is resting upon the Middle Layer, there is almost always a transitional zone in which unpatinated as well as patinated artifacts occur"…
(4) Craddock P, 2009 Scientific investigation of copies, fakes and forgeries, Elsevier  pp 268
Mark Jones, British Museum, in:Fake? The art of deception, Jones(ed.) University of California Press ( with additional parts of : Craddock/Barker) 1990
(5) Rottländer 1975 Post-depositional surface modifications PDF
(6) G.J. van Noort, strandproefhyaliet


S. Hazzledine Warren 1900. V.—Palæolithic Flint Implements from the Chalk Downs of the Isle of Wight and the Valleys of the Rivers Western Yar and Stour. Geological Magazine (Decade IV), 7, pp 406-412
Moganite, a neglected polymorph of Silica  by Graham wilson, 2002- article  ( many references on the subject)
 *** Heemkundekring Velpeleven Boutersem Jaargang 1999, nummer 6 "Prehistorie: ook bij ons!" ( " …  Eén zijde heeft een blauw-witte patina, de andere zijde is slechts zeer licht gepatineerd  )
Hiscock, Peter, 1985 The need for a taphonomic perspective in stone artefact analysis  PDF ; Queensland Archaeological Research 2:82-95.
WD Mokokwe – 2007 The Goldsmith’s archaeological assemblage PDF ( about weathering of artifacts within the assemblage)
The Rossnaree archaeological project blog ; The low-tech ‘art’ of field walking (surface-collection survey) - article
(7) See: V. Rots, Hafting traces on tools PDF (KU Leuven) ( )  JONG-PALEOLITHICUM TE KANNE EN TE ORP PDF

1 comment:

  1. Hello,

    Thought you might be interested in this recent paper:

    Glauberman, P.J. and R. M. Thorson 2012. Flint Patina as an Aspect of “Flaked Stone
    Taphonomy”: A Case Study from the Loess
    Terrain of the Netherlands and Belgium. Journal of Taphonomy 10, 21-43.


    ReplyDelete