Rare blue pigments: from lapis lazuli to YInMn Blue

1 · Why blue is difficult

Earth pigments are abundant because iron oxides are abundant: yellows, reds, browns and blacks can be dug up and washed. A blue requires a material that absorbs across the long-wavelength half of the visible spectrum while leaving the short end intact — a much narrower electronic requirement, and one that most cheap minerals do not meet.

Historically that left three routes: grind a rare blue mineral, synthesise a blue compound, or fake it with a dye on a substrate. Each route produced pigments with characteristic weaknesses — scarcity, instability in certain binders, or toxicity — and those weaknesses are still what a specifier is choosing between.

2 · Six blues compared

CLAIM TYPES ON THIS PAGE — ESTABLISHED FACT: COMPOSITION AND CHEMISTRY, CITED PER ROW. HISTORICAL CONTEXT: THE ERA COLUMN, WHICH GIVES CONVENTIONAL PIGMENT-HISTORY DATING AND IS NOT A SOURCED MEASUREMENT. BADAR COMMERCIAL FACT: THE AVAILABILITY COLUMN, WHICH DESCRIBES HOW WE HANDLE AN ENQUIRY AND NOT STOCK WE HOLD.

3 · Lapis and natural ultramarine

Lapis lazuli is the rock; lazurite is the mineral inside it that carries the colour; natural ultramarine is the pigment prepared from it. The distinction matters commercially, because simply grinding lapis gives a greyish blue — the calcite and pyrite that make the stone attractive as a gem dilute it as a pigment^[6].

The historical extraction methods existed to separate lazurite from that matrix, and they are slow and lossy. That, not the rarity of the stone, is why the pigment was famously expensive — and why a modern quotation for natural ultramarine reflects labour as much as material^[6].

Synthetic ultramarine is chemically close and available at a small fraction of the cost. For most work it is the correct answer. Natural ultramarine is specified where the material itself matters — conservation, analytical matching, or a project where provenance is part of the brief.

4 · What is obtainable today

Three of the six are ordinary commerce: Prussian blue, synthetic ultramarine and — with attention to its classification — cobalt blue^[7]. YInMn Blue is obtainable but priced by its indium content, so it is specified where its stability or near-infrared reflectance earns the difference rather than as a general-purpose blue.

Azurite and natural ultramarine are special-order materials whose availability moves with supply of the raw mineral. Egyptian blue is produced in small quantities for conservation and research rather than as an industrial colourant. Where any of these is not the right answer, the honest response is a modern equivalent, named as such.

5 · Choosing one for a project

• If the requirement is durability under sun

  Start with inorganics. Ask specifically about weathering data for the grade, and about near-infrared behaviour if the surface will run hot.

• If the requirement is tinting strength per kilogram

  Organic blues will win on cost in use. The trade is heat and, depending on grade, long-term lightfastness in tints.

• If the requirement is historical accuracy

  Specify the mineral and the particle size range, and expect availability rather than price to be the constraint. Send the analytical evidence you are working from.

• If the requirement is an appearance you have seen

  It may not be a pigment at all. Highly saturated automotive blues are often interference effects — see structural colour.

• YInMn Blue pigment
• Natural ultramarine
• Historical pigments
• Rare pigment sourcing

References

Each reference supports only the claims marked with its number. Era values in the comparison table are conventional pigment-history dates given as context; the references cover composition and chemistry, not dating. Availability statements describe how BADAR handles an enquiry and are not drawn from any of these sources.

1. [1] Panagopoulou A., Karanasios K. & Xanthopoulou G. “Ancient Egyptian Blue (CaCuSi₄O₁₀) pigment by modern solution combustion synthesis method.” Eurasian Chemico-Technological Journal 18(1), 31–37 (2016). DOI 10.18321/ectj390. doi.org/10.18321/ectj390
2. [2] Lluveras A., Boularand S., Andreotti A. & Vendrell-Saz M. “Degradation of azurite in mural paintings: distribution of copper carbonate, chlorides and oxalates by SRFTIR.” Applied Physics A 99(2), 363–375 (2010). DOI 10.1007/s00339-010-5673-5. doi.org/10.1007/s00339-010-5673-5
3. [3] Kraft A. “The history of Prussian blue.” In Prussian Blue-Type Nanoparticles and Nanocomposites, 1–26. CRC Press (2019). DOI 10.1201/9780429024740-1. doi.org/10.1201/9780429024740-1
4. [4] Ali A., El Fadaly E. & Ahmed I. “Near-infrared reflecting blue inorganic nano-pigment based on cobalt aluminate spinel via combustion synthesis method.” Dyes and Pigments 158, 451–462 (2018). DOI 10.1016/j.dyepig.2018.05.058. doi.org/10.1016/j.dyepig.2018.05.058
5. [5] Smith A. E., Mizoguchi H., Delaney K., Spaldin N. A., Sleight A. W. & Subramanian M. A. “Mn³⁺ in trigonal bipyramidal coordination: a new blue chromophore.” Journal of the American Chemical Society 131(47), 17084–17086 (2 December 2009). DOI 10.1021/ja9080666. pubmed.ncbi.nlm.nih.gov/19899792
6. [6] Favaro M., Guastoni A., Marini F., Bianchin S. & Gambirasi A. “Characterization of lapis lazuli and corresponding purified pigments for a provenance study of ultramarine pigments used in works of art.” Analytical and Bioanalytical Chemistry 402(6), 2195–2208 (2012). DOI 10.1007/s00216-011-5645-4. pubmed.ncbi.nlm.nih.gov/22203372
7. [7] Substances restricted under Annex XVII to REACH. European Chemicals Agency. echa.europa.eu/substances-restricted-under-reach