Rendiconti Lincei. Scienze Fisiche e Naturali
https://doi.org/10.1007/s12210-023-01153-5
REVIEW
Egyptian blue, Chinese blue, and related two‑dimensional silicates:
from antiquity to future technologies. Part A: general properties
and historical uses
Marco Nicola1,2 · Roberto Gobetto1 · Admir Masic3
Received: 4 November 2022 / Accepted: 2 March 2023
© The Author(s) 2023
Abstract
The ancient Egyptian blue pigment was developed over 5000 years ago and was used extensively for around four millennia
until its use mysteriously declined dramatically during the Early Middle Ages. It recently attracted a lot of attention along
with some related materials, leading to a fast-growing number of applications in fields, such as sensors, solar concentrators,
energy-saving, and medicine. The new surge in interest began in 1996 with the discovery of their intense NIR photoluminescence
that surprisingly can be triggered even by visible light. In 2013, the possibility of exfoliating them and producing
NIR luminescent nanosheets was established, expanding the family of 2D nanomaterials. More recently, the discovery of
their high antibacterial effects and biocompatibility, and very promising optical, electric and magnetic properties, has further
boosted their applications. The characteristics of Egyptian blue are due to its main component: the very stable crystalline
compound CaCuSi4O10.
This tetragonal sheet silicate is the synthetic analogous of the rare cuprorivaite mineral. In Part A of
this review, we summarize the historical uses and main properties (i.e., composition, structure, color, stability, luminescence,
and biological activity) of cuprorivaite and related 2D silicates, i.e., BaCuSi4O10
(the main constituent of the ancient pigment
Chinese Blue), BaCuSi2O6
(the main constituent of the ancient pigment Chinese Purple), SrCuSi4O10
(synthetic analogous
of wesselsite) and BaFeSi4O10
(synthetic analogous of gillespite). The Part B of the review will focus on the modern rediscovery
of these materials, their modern synthesis and exfoliation, and the innovative applications based on their properties.
Keywords Egyptian blue · Han blue · Han purple · Cuprorivaite · Wesselsite · Gillespite · Luminescence
1 Egyptian blue, Chinese blue, and related
2D silicates
Egyptian Blue (EB) is an artificial blue pigment of mineral
origin used also to mold small objects thanks to its vitreous
ceramic nature (Lucas and Harris 1962; Chase 1971;
Delamare 1997). It was developed in Egypt during the Early
Bronze Age, more than 5000 years ago (Corcoran 2016), and
is considered to be the first true synthetic pigment ever produced
by humans (Riederer 1997; Warner 2011; Corcoran
2016; Greco 2022).
EB largely owes its color and its extraordinary features to
the crystals of CaCuSi4O10
(also CaO·CuO·4SiO2 or calcium
copper tetrasilicate) that form during its manufacturing. This
compound is the artificial analogous of a mineral very rare
in nature, i.e., cuprorivaite (Mazzi and Pabst 1962). Natural
cuprorivaite (see Fig. 1) forms likely under hydrothermal
conditions, i.e., high temperature and high-pressure conditions
that occur beneath the Earth's surface in the presence
of water (Giester and Rieck 1994; Warner 2011; Johnson-
McDaniel et al. 2015; Cairncross and Rumsey 2022). It was
identified as a new mineral by Minguzzi in 1938 on a rock
specimen from Mount Vesuvius (Minguzzi 1938). Some
20 years later, it has been correlated to the chemical composition
of EB (Schippa and Torraca 1957; Pabst 1959; Mazzi
* Marco Nicola
nicola@adamantionet.com
* Roberto Gobetto
roberto.gobetto@unito.it
1 Department of Chemistry, University of Torino, Via Giuria,
7, 10125 Turin, Italy
2 Adamantio Srl, Science in Conservation, Via Napione, 29/A,
10124 Turin, Italy
3 Department of Civil and Environmental Engineering,
Massachusetts Institute of Technology, Cambridge,
MA 02139, USA