Short answer
They are iron-bearing earths, and their colour comes from two minerals: yellow-brown goethite and red haematite, darkened by manganese in sienna and umber. Heating turns the first into the second, which is how raw sienna becomes burnt sienna and how yellow mine waste at Falun becomes red paint. The place names record where a pigment was dug or sold, not what the place looks like — and for umber even the link to Umbria is disputed.
An ochre is clay and sand coloured by iron. The Roussillon study that this page's table comes from analysed its samples as three iron-bearing phases — goethite, haematite and kaolin — and summarises the literature in one line: haematite is the chromophore for red and goethite for yellow, modified by exact composition and particle size. Sienna adds a small amount of manganese oxide, which darkens it below ochre; umber carries more manganese again and is browner and cooler. The whole family of raw and burnt earths is therefore a few oxides in different proportions, which is why they recur wherever iron-rich clay weathers at the surface.
Goethite and limonite hold water in their structure. Drive it off and they convert towards haematite, and the colour moves from yellow to red. The Falun paint maker describes this stage by stage for its own kilns: the washed and settled sludge begins to turn from yellow to red as it dries at around 150 °C, becomes light red at about 500 °C when the limonite converts to iron oxide, darkens at 700 °C and heads towards black above 950 °C, with samples checked every hour to hit the shade. Burnt sienna and burnt umber are the same reaction applied to earths that also contain manganese, giving reddish brown and very dark brown.
This is also why 'Falu red' is a family of shades. The colour is set by kiln temperature, and the maker notes that lighter and darker reds have been in favour at different times.
Six samples collected on the Sentier des Ocres near Roussillon were sieved, and their CIELAB coordinates were calculated from measured reflectance under illuminant D65 for the 10° observer. Lightness ran from about 36 to 61, a* from about 13 to 20 and b* from about 25 to 40. The authors found b* rising with goethite content and a* rising with haematite content. The table adds hue angle and chroma, calculated here from the published a* and b*: the two samples with almost no haematite sit near 70°, towards yellow, and the haematite-rich samples near 53° to 56°, towards orange-red. It is a rare case of a place-named colour with numbers attached — and the numbers describe sieved powder from one trail.
Sienna takes its name from Siena, where the earth was produced during the Renaissance. That is a statement about a trade, and it does not follow that Siena's buildings are sienna-coloured; UNESCO's statement of value for the historic centre does not describe the city's colour, so the places section records none. Umber is weaker still as geography. Some sources derive the name from Umbria and others from the Latin umbra, shadow, and the pigment has been produced chiefly in Cyprus. A pigment named after a place tells you where merchants bought it, sometimes only what they called it.
Falu red is the best documented of these pigments because its maker and the mining museum at the World Heritage site both describe it. Ore too poor in copper was sorted onto waste heaps, where its iron sulphides weathered into yellow limonite; washing, settling and roasting turn that into red pigment. The maker dates industrial production to 1764 and cites a royal instruction of 1573 to paint castle roofs red with material from the mine. The paint moved from noble houses in the seventeenth century to farms in the nineteenth. Here a place really did colour a country, but by supplying paint: the red of a Swedish barn says nothing about the ground it stands on.
| Sample | Goethite % | Haematite % | L* | a* | b* | Hue angle (calculated) | Chroma C* (calculated) |
|---|---|---|---|---|---|---|---|
| 2 | 41.1 | 43.2 | 61.4 | 19.8 | 29.6 | 56° | 35.6 |
| 8 | 38.6 | 37.3 | 45.3 | 17.7 | 25.0 | 55° | 30.6 |
| 7 | 63.2 | 30.0 | 36.5 | 20.3 | 26.7 | 53° | 33.5 |
| 6 | 65.4 | 10.9 | 51.5 | 12.7 | 26.8 | 65° | 29.7 |
| 3 | 88.5 | 3.2 | 54.8 | 13.1 | 34.4 | 69° | 36.8 |
| 4 | 85.6 | 1.5 | 48.1 | 14.0 | 40.3 | 71° | 42.7 |
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactModerate evidence· Roussillon, Vaucluse, France
In six ochre samples from the Sentier des Ocres near Roussillon, CIELAB b* correlated with goethite content and a* with haematite content; lightness ranged from 36.5 to 61.4, a* from 12.7 to 20.3 and b* from 25.0 to 40.3 on the 20–50 µm fraction.
Measured: Six field-collected ochre samples. Method: Mössbauer spectroscopy for mineral phases; CIELAB calculated from reflectance for CIE D65 and the 10° observer.
Caveat: A preprint with six measured samples of sieved pigment from one site; not a measurement of painted or rendered surfaces.
Source: Relationship between Colours of Ochre from Roussillon and Content of Iron-Bearing Minerals
Colourwise analysisModerate evidence
Across the six Roussillon samples the CIELAB hue angle lies between about 53° and 56° in the three samples with most haematite and between about 69° and 71° in the two with almost none.
Based on: Hue angle calculated by Colourwise as atan2(b*, a*) from the a* and b* values in the study's Table 3 (reflectance method); see the table on this page.
Caveat: Six samples; hue angle inherits the study's measurement conditions and says nothing about lightness.
Source: Relationship between Colours of Ochre from Roussillon and Content of Iron-Bearing Minerals
FactStrong evidence· Falun, Sweden
Falu red pigment is made from weathered low-copper ore from the Falun mine: limonite in the washed fines is dried and burned, turning light red at about 500 °C, darker at 700 °C and towards black above 950 °C.
Caveat: The manufacturer's description of its own process.
Source: The Unique Pigment; Falu Rödfärg — modern in all times (Mining Museum exhibition)
FactModerate evidence
Sienna is an earth pigment of iron oxide with some manganese oxide, named after Siena where it was produced in the Renaissance; heating dehydrates its limonite and goethite partly to haematite, giving burnt sienna.
Source: Sienna
FactLimited evidence
The name umber is attributed by some sources to Umbria and by others to the Latin umbra, shadow, and the pigment has been produced mainly in Cyprus.
Caveat: A reference work reporting a disagreement between sources; the etymology is unresolved, so the link to the region should not be asserted.
Source: Umber
Colourwise interpretationLimited evidence
A pigment's place name records where it was dug or traded and is not evidence for the colour of that place's buildings.
Based on: The sources located describe sienna as produced at Siena and Falu red as exported from Falun; none describes Siena's or Falun's townscape in those colours, and UNESCO's statement for Siena does not mention colour.
Caveat: An absence of evidence in the sources read, not a survey of either town.
Reviewed 6 October 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.