Geologically, we can define ochres as earthy, metal oxide- or metal oxide hydroxide-rich deposits which form in the surface or near-surface environment. The most commonly encountered ochreous deposits are iron-rich, although copper and cobalt ochres have also been exploited for pigment use, and manganese ochres (wads) will be considered separately below. Naturally occurring ochres are by definition impure deposits containing a mixture of mineral components, commonly quartz, carbonate, clays and/or micas as well as metal sulphides. They are encountered as primary ochres, lying in close association with ore bodies or as secondary ochres subsequently concentrated in sediments and soils. Commonly these are soft and friable and therefore easily excavated and processed.
In the world of pigments and art history, the term “ochre” generally refers to iron oxide and oxide hydroxide rich powders with variable amounts of manganese oxides (Eastaugh et al. [9
] and references therein). Red ochres are dominated by hematite and yellow ochres are typically dominated by goethite, though jarosite group mineral-rich yellow ochres are of local importance. The definition of ochres also includes ferrihydrite-rich ochre deposits formed as the result of natural acid rock drainage (NARD) and acid mine drainage (AMD) which tend to revert to goethite [10
]. Such deposits are concentrated in streams and rivers and their locations would have been remarkable as well as colourful to pre-industrial eyes (Figure 1
). The use of ferrihydrite as ochre pigments has been poorly documented, primarily as it readily converts to goethite over time, but it is extremely likely that NARD deposits would have been used to procure colour.
Yellow goethite ochres can be heated and are easily converted to red ochre of various shades when exposed to temperatures in excess of ~250 °C. Structurally disordered hematite has been encountered in the archaeological record [12
]. Analyses of experimentally burnt ochre conducted by the author, Spike Bucklow, Onya McCausland and David Dobson (pers comm
) using XRD, have shown that a high purity goethite ochre converted to well-crystallised hematite after 45 min burning in an open air, wood fire, disputing the claims that “disordered” hematite is evidence for primitive heat treatment [13
]. As such, evidence of ochre burning in the archaeological record may be impossible to determine. David et al. [14
] analysed ochres from the Egyptian site of Tell el-Amarna and found that yellow ochre pigments contained impurities of well-crystallised carbon, whereas red pigments were red ochre containing impurities of amorphous carbon. The interpretation of these results is that the red ochre was a burned version of the yellow. Controlled modification of colour through heating ochres has become standard practice within the historical period paint manufacturing industry. The colour of natural “raw” ochres is related to their composition (relative proportions of hematite and goethite ± manganese oxides; see Elias et al. [15
]) and also particle size and the uniformity of particle size. The latter property has been shown to have a marked effect on the extensive range of colour exhibited by natural ochres collected from Clearwell Caves in the Forest of Dean, England [16
A major problem with red ochres is that they are extremely difficult to provenance, especially when highly processed. The presence of quartz or carbonate can be helpful in differentiating broad sedimentary environments, as can crystal habit (if preserved), colour (if not heat treated) and particle size (if not overly ground). A good field knowledge of the character and mineralogy of preserved ochre deposits in the vicinity of an archaeological site can be instrumental in securing provenance of local use [18
]. However, ochre had status in societies and as a commodity it was traded over long distances [19
]. White et al. [20
], in an important piece of work at the Puritjarra rock shelter in central Australia, was able to provenance ochres sourced regionally based on a cluster analysis of major minerals and trace elements, made on both ochres sourced at the site and known Aboriginal ochre pits across Australia. A similar study was made on a smaller scale by Eiselt et al. [21
] from Hohokam and O’odham prehistoric sites in Arizona; ochre played a key role in the societies of the Gila River Valley, where it was used for body paint, rock art, other aspects of craft production and in mortuary contexts.
3.1.1. Red Ochre
The use of red, hematite-rich (Fe2
) ochres as pigments is global and they have been recorded in all works of art of all periods and traditions. As a pigment, it has been in continual use from the Pleistocene to the present day. The processing of geological ochres to transform them into ochre pigments is straightforward and involves a chaîne opératoire
involving removal of larger impurities (including plant roots and other organic contaminants), grinding, sieving and/or levigation before adding to a medium to produce a paint. Ochre-derived pigments were and are also widely used as body decoration and sun protection, medical use, adhesives and as paints (slips) used to decorate ceramics as both pre-and post-firing treatments. Partly due to its preservation, evidence of intentional uses of ochre are associated with almost all excavations of both anatomically modern humans (Homo sapiens
) globally and with Neanderthals in Europe. Arguably, in addition with stone suitable for tool making, the procurement, preparation and application of ochres is arguably the earliest exploitation of Earth materials and the burning of ochres to modify their colour is the earliest form of pyrotechnology. In recent and modern hunter-gatherer societies such as the Kalahari Bushmen, Australian Aboriginals and the Peoples of the Pacific Northwest Coast and southwest USA, ochres and particularly red ochres have great significance in representing abstract concepts such as vitality, birth/rebirth and fertility, and there is reason to suggest that Palaeolithic societies would have imbued red ochres with the same powers. However, it should also be remembered that the colour red is bright and noticeable and deposits of red ochre would have been ubiquitous and obvious in a (pre-agrarian and pre-urban) landscape and such localities indeed may have been associated with supernatural properties [20
]. Red ochre was the colour of the Palaeolithic and in all cases described below, hematite was the predominant chromophore in these pigments. To provide a comprehensive review of the global and temporal use of iron ochres in pre-Neolithic archaeology is well beyond the scope of this paper, nevertheless I will endeavour to cover some key Palaeolithic sites and discoveries.
Numerous early uses by humans from the Middle Stone Age (MSA) of Africa (280–50 ka) include evidence for ochre mining and processing in southern Africa [22
]. Henshilwood et al. [23
] excavated at the 100 ka Blombos Cave site in South Africa where clear evidence of red ochre processing and pigment preparation is in evidence. Raw ochre, grindstones, palettes and Haliotis
sp. shells used for storage have been discovered.
Red Ochre was excavated in the Pleistocene (Middle Palaeolithic) age. These sites have been excavated in the Maastricht-Belvédère loess and gravel pit. Sediments here are associated with MIS 7, dating from 250 to 200 ka. These strata are relatively iron-poor, and ochres do not occur within this sedimentary sequence, but fifteen, very pure, red hematite “concentrations” with sharp margins with the enclosing sediments were found in association with flint tools and debitage. Roebroeks et al. [24
] have interpreted these as drops of ochre paint, perhaps used on bodies or for some other unknown purpose. If this is the case, then this is the earliest use in Europe of ochres, with a date equivalent to earliest uses in Africa. In Eurasia, the Mousterian period (160–40 ka; Late Pleistocene) is predominantly associated with a few sites in the Near East showing a brief period of occupation. At Qafzeh Cave in Galilee, humans were buried in association with lumps of red ochre as well as Glycymeris
sp. shells with red ochre stains on the concave surfaces. These shells were worn as body ornaments and could potentially also have been used as pigment containers. This deposit has been dated to 92 ka [25
]. It is worth noting that mollusc shells have played a huge role in the history of pigments, being universally used for the storage of paints and pigments.
Other findings of use of ochre are few and far between. A recent and very important discovery has been made in the dating of parietal art (cave painting) in Iberia. “Art” as we would currently define the word is associated with the cognitive abilities, but a number of decorative schemes appear to date to the later Mousterian which requires revolutionary rethinking of this concept. Hoffman et al. [1
] have ascribed red ochre geometric designs, hand stencils and painted speleothems in three cave sites (La Pasiega, Cantabria; Maltravieso, Extremadura and Ardales, Andalucia) a date of 64.8 ka. More typical examples of Mousterian, ochre use are deposits found at Fumane Cave in Liguria, Italy. Peresani et al. [26
] report an ochre coated fossil shell (Aspa marginata
) possibly worn as a personal ornament in deposits dating from 45 to 48 ka. The fossil is sourced from a low-iron clay, implying that the ochre coating was intentionally applied.
It is generally accepted that migration out of Africa occurred c. 70 ka, and rapidly spreading eastwards throughout Asia and Oceania and reaching Europe after ~50 ka. These people brought with them a knowledge of the technology of ochre processing and we see a blooming of sophisticated artistry from 40 to 30 ka. In the Far East, Pitarch-Martí et al. [27
] have analysed red-stained, ostrich shell beads from the 31 ka Shuidonggou Locality 2 site and found them to be coated with a red ochre composed of hematite with impurities of feldspars, micas and clays. An important site in the Northern Territories of Australia is the Puritjarra rock shelter where there is evidence of processing of both local and imported red ochres continually from 32 ka up until the present day [20
]. However, it is in western continental Europe that Palaeolithic parietal art is perhaps best known (although cave art is not limited to this region, [22
]). During the period of ~35–12 ka we see an expansion of the Palaeolithic palette to include black and this is discussed in more detail below. However extensive red ochre deposits are available in the French and Spanish landscapes to furnish cave painters with more the sufficient materials, those precise provenance regions have not been identified [28
The Upper Palaeolithic is particularly associated with so-called ochre burials, particularly so in regions where parietal art does not exist. One of the earliest of these is the Red “Lady” of Paviland (26 ka, [30
]; Figure 2
) in South Wales, UK and also remarkable is the double child burial at Sunghir in Russia. The latter is an exceptional example of an ochre burial dated to ~24 ka [31
]. In these and other similar occurrences throughout Europe, the bones are encrusted with hematite. It is likely that this is derived from ochre-stained clothing or shrouds rather than (as once thought) that the bodies were sprinkled with red ochre [30
]. In the case of the Pavilland burial, precise provenancing of the ochre has been possible and it was shown to be locally derived [18
By the Neolithic, the painter’s palette had expanded considerably, and this will be discussed below. However red ochre was still an important component. A great deal of red ochre is used for domestic decoration at the 10-ka site of Çatalhöyük [32
]. We see its use in complex religious architecture of Malta. Attard-Montalto et al. [33
] has identified ochres derived from terra rossa soils and deposits in karstic fissures as paint materials during the unique Neolithic Temple Period of Malta (4th–2nd Millennia BC).
By the Bronze Age, the pigment was in use in Mycenaean and Minoan wall paintings [34
], in Egyptian Art [14
]. Ochres were in use in the far east. An unusual use as cosmetic sticks, wherein red ochres was mixed with dried cattle heart was discovered in Xiaohe Cemetery (1980–1450 BCE) in Xinjiang, China [38
During the European Classical period we see for the first time, a clear, documented craft specialisation of painters and artists, with red ochre being considered part of the standard palette of artists and the costs of similar, so called “austere” pigments was included in the commission price of the artist, a practice that was to continue on into the European Renaissance. The Roman author Pliny the Elder reports known ochre sources and trade links, indeed much of his work referencing the Greek author Theophrastus, showing there was a continuum in use of these materials during the Iron Age and into the early Medieval period. As such, we see red ochres as standard and widely used pigments in both Etruscan and Roman painting [39
At the 9th–12th Century CE buildings at the Angkor Wat temple complex in Cambodia, polychromy wall painting is uncommon and the palette relating to the early period of construction is limited to red, orange and carbon black (soot). Most walls are painted red using hematite red ochre [44
]. The ochre was sourced from the surrounding laterite deposits, which are also the main building stones used for the construction of these temples.
3.1.2. Wads: Manganese Ochres
The obvious choice of black pigment for any society is the easily produced and high purity carbon-based black in the form of soot. Alternatively, woody plant material is easily charred (as are bones and ivory) to produce high quality black pigments. Therefore, it is astonishing to find that some of the earliest evidence of the use of black pigments, from the Mousterian of Europe are mineral blacks in the form of manganese ochre or wad [45
]. Wad is an old English miners’ term for black earths [47
] which is primarily applied to manganese-rich earths but may also be applied to deposits of graphite. Wads are typically composed of complex assemblages of manganese oxide and hydroxide minerals plus or minus iron oxides [9
]. Provenance of wads has proven to be hugely problematic as they are poorly recorded in the geological literature and not well-recognised in the landscape. Nineteenth century sources [48
] described workable deposits of pigment-grade wad in Devon, Somerset and Derbyshire in the UK. Heyes et al. [45
] report “blocs” of manganese dioxide earth with clear use-wear from sites in France. This substance also has properties which make it useful in fire-lighting and so it was not necessarily used in this context as a pigment. Sources of manganese oxide ochres are known from the French Massif Central [45
Roldan et al. [12
] have identified both manganese oxide black pigments as well as charcoal on a series of painted, portable “plaquettes” excavated at Parpalló Cave in SE Iberia, dating from between 26 and 11 ka using Energy Dispersive XRF (EDXRF). In Middle to Upper Palaeolithic parietal art in the caves and abris of France and Iberia, created by anatomically modern humans, used a palette of primarily red ochre, very minor yellow ochre and black. These cave paintings are the most well-known manifestation of ice-age art. Developments in radiometric dating in the early 21st Century allowed for precise radiocarbon dates to be made of charcoal fragments included in the painted surfaces. Although assumed to fall in the Magdalenian Period (12–17 ka) which is chronologically accurate for Lascaux, Niaux and Altamira and Ekain Caves, Valladas et al. [49
] have shown that comparable painting schemes were created as early as 29–35 ka at Chauvet Cave, with a continuum of painting (and perhaps retouching of paintings) in the intervening 20,000 years at a large number of cave sites. Black pigments have been analysed by Emile Chalmin and co-workers and are published in a series of articles [51
]. Charcoal was used as a black pigment in parietal art, but mainly for drawing outlines. Black paint fills have been identified as containing manganese oxide pigments and wad “crayons” have been excavated from several caves. Due to these phases being opaque, PLM is an inappropriate technique for the characterisation of many black pigments, and analyses were therefore confirmed by TEM, XRD, IR and Raman spectroscopy and SEM/EDX. The manganese minerals pyrolusite, romanechite, hollandite, cryptomelane, todorokite, manganite, hausmannite, nsutite, ramsdellite and groutite have been determined from the Magdalenian (17–12 ka) sites of Lascaux, Ekain, Gargas, Labastide, Combe Sauniere [51
] and Roucador [55
]. There is no evidence to suggest that these wads were burned prior to use [53
Provenance of these minerals is also problematic as wad sources are poorly described and composed of complex mixes of mineral phases. Identification of phases such as groutite and nsutite in these western European paintings have been highlighted as the first occurrence of these mineral phases in the regions. A note of caution is required in the interpretation of such data. To ascribed rarity and therefore novelty to such discoveries is unwise. This is unlikely to be the case. The range of known comparanda is simply an artefact of the available geological and mineralogical literature. From the point of view of a field geologist, there is little reason to focus on this level of detail in the analysis of small-scale mineral deposits.
Using Raman spectroscopy, Sepúlveda et al. [56
] identified manganese oxide pigments in Epipalaeolithic to Neolilithic (10–3.7 ka) Chile. The Chinchorro hunter-gathers used a manganese black composed of hollandite and cryptomelane for the painting of mummy wrappings and manganite, pyrolusite and cryptomelane were found in rock art from the Tangani and Pampa el Muerto Highlands. These were provenanced to Los Pumas in the Atacama Desert. In Argentinian Patagonia, Wainwright et al. [57
] identified manganese oxide blacks at the 9 ka rock art sites of Cueva de las Manos and Cerro de los Indios.
Evidence of manganese oxide black pigments in Iron Age art is scarce. Kakoulli [58
]) has identified pyrolusite in Roman wall paintings at Nea Paphos in Cyprus. The main pigments used from this period onwards were carbon-based blacks, soots and chars.
Extensive discussion of the use of manganese oxide black as slips, paints and glazes in the literature on archaeological ceramics which is well beyond the scope of this paper. Manganese oxide minerals encountered in paintings are summarised in Table 1
3.1.3. Yellow Ochre
Yellow ochres, which are either rich in goethite (FeO[OH]) or the jarosite-group minerals, are apparently uncommon in works of art prior to the later Neolithic. However, as the palette expanded beyond red and black, yellow ochre became a standard artists’ material and particularly the use of goethite-rich yellow ochres became temporally and globally common. Occurrences are too abundant to cite, but significant uses of this pigment are summarised below.
Wainwright et al. [57
] have found goethite yellow ochres at the 9 ka rock art sites of Cueva de las Manos and Cerro de los Indios in Argentina. Goethite has also been identified in rock art in Southern California [59
]. Both goethite and jarosite ochres have been found in Egyptian painting from the Old Kingdom to the Ptolemaic period [14
]. Wong et al. [64
] have shown that the yellow background to the paintings in the Tomb of Tutankhamen in the Valley of the Kings (Tomb KV 62) are goethite yellow ochres. In the northern Mediterranean, goethite is recognised from Minoan and Mycenean Art [34
], Macedonian tomb paintings [65
] and goethite ochre has been analysed on Hellenistic terracotta figurines [66
] and for painting the skin of a 4th Century BCE marble statue of a male youth by Abbe et al. [67
]. Yellow ochre was one of the “austere” pigments of Pliny’s palette. Goethite yellow ochres have been found across the Roman Empire in all contexts [41
Stodulski et al. [72
] have identified goethite-rich ochres at 6th Century CE Persepolis and Holakooei and Karimy [73
] have found goethite ochres in early Islamic wall paintings in Central Iran, and Gebremariam et al. [74
] have found goethite yellow ochres on Christian wall painting sin Ethiopia. In China, goethite ochre is used at the Tang Dynasty Li Shimin painted tomb [75
]. Goethite ochres were used at the Bhimbetka rock shelters in India [76
The jarosite group minerals (jarosite; KFe3+3
, natrojarosite; NaFe3
and hydronium jarosite; [H3
), themselves part of the alunite supergroup, are globally common but comparatively poorly described in the geological literature, leading to the misapprehension that jarosite group minerals are “rare” when encountered in the analysis of works of art and on archaeological artefacts. Indeed, jarosite ochres are locally abundant and their bright lemon-yellow colour makes them readily attractive to people prospecting for pigments. The author has collected almost pure jarosite ochres from locations as diverse as Sia Copper Mine, Cyprus and Kimmeridge Bay on the South Coast of England. The discovery of jarosite in meteorites derived from Mars has sparked more recent geological interest in these minerals and their petrogenesis in supergene environments and in association with mine waste [77
]. Jarosite group minerals are readily distinguished from goethite using PLM due to the former’s low birefringence and platy crystal morphology and are differentiated using Raman spectroscopy [61
Dutrisac et al. [77
] claims that jarosite group minerals were being exploited at Rio Tinto in Spain from 1200 BCE. Jarosite yellow ochres have been identified on painted objects from the 9 ka site of Takarkori, Libya by di Lernia et al. [82
] and jarosite has also been detected in Australian Aboriginal rock art in the Kimberley region [83
Jarosite was first recognised as a mineral pigment in Egyptian contexts and it is in art of this region that the pigment is best known [60
], leading its use to be considered as a local specialisation. The discovery of jarosite in Roman and Middle Eastern contexts to have led to this pigment being interpreted as an Egyptian import. However, identifications are still not particularly common; hydronium jarosite has been identified amongst Roman painting materials at Pompeii [40
] and jarosite and alunite are used in yellow paints on wall paintings from the Early Islamic (9th–11th Century CE) site of Nishapur in Iran [86
]. It is likely that reanalysis of some yellow earth pigments generically described as “yellow ochre” may transpire to be composed of jarosite group minerals.