According to American archaeologist J.M. Kenoyer, chrysoprase (
Similarly ancient chrysoprase artifacts came from the Western Asia, precisely, from the areas of present-day Syria, Arabian Peninsula, Egypt, and Mesopotamia. The most important city-state of southern Mesopotamia in the 4th millennium BC was Uruk. Before the World War II and then in the 1980s, it became the target of intensive archaeological excavations. Among numerous stone artifacts, single objects made of chrysoprase were found, as well (Finkbeiner 1991; Moorey 1999). Likewise, old Mesolithic artifacts were found in the Sudety Mts. in Poland (Přichystal 2013). Another example is a Neolithic bead made of chrysoprase, found during excavations in Syria, dated to the late 8th millennium BC (now in the collection of the Metropolitan Museum, in New York). On the other hand, chrysoprase beads and other ornaments made of carnelian, lapis lazuli, and turquoise from the Shakhr-i-Sokhta and the Tepe Hissar workshops (now Iran), discovered and studied in the early 20th century by Hungarian archaeologist Aurel Stein, were dated to the 3rd millennium BC. A group of Italian archaeologists led by Professor Maurizio Tosi also carried out excavations in that area. Their findings indicated that in the ancient times, chrysoprase was relatively rarely used for making ornaments, which explains only the single stone objects of that type found on the examined archaeological sites (Biscione et al. 1974).
Possible source of raw material for ancient sculptors may have been deposits located in the Jebel al-Ma’taradh massif, near the village of al-Ghail, in the territory of the Ra’s al-Khaimah emirate (now the member of the United Arab Emirates), discovered by French archaeologists (Charpentier et al. 2017). An exceptionally valuable find was an axe handle made of chrysoprase from the Suhaila 3 site, with a doubly convex facing section and strongly sharpened edges. Chrysoprase artifacts were encountered as far as 300 km from the Jebel al-Ma’taradh. This is significant fact because so far, in the archaeological literature of the United Arab Emirates and the Oman Peninsula, no record has been encountered of chrysoprase and other silica varieties in the area, let alone the existence of the Jebel al-Ma’taradh deposit itself.
In ancient Egypt, from Predynastic times and later, in the Old, Middle and New Kingdoms until the Greco-Ptolemaic and Roman periods, precious and decorative stones were highly valued. Chrysoprase necklace beads from 5,300 BC, originated from very early stage of ancient Egyptian civilization, are some of the oldest archaeological items taken from unnamed tombs in the Upper Egypt (Rapp 2002). It seems that chrysoprase was not a common raw material for manufacturing of small stone artifacts in ancient Egypt due to the lack of local deposits (Aston et al. 2000). However, it was occasionally imported for making the scarabs, especially their specific sepulchral variety – the “heart scarabs”. These items were symbols of rebirth after death, a sign of resurrection, therefore, these were placed near the heart of the deceased, under the rolls of bandages with which the mummy was wrapped (Śliwa 2003; Chudzik 2016).
In the surviving Theban manuscripts, dated to the end of the 3rd century AD (i.e., the end of the Ptolemaic-Roman period), in the second part of the so-called “
The most important legacy of ancient Greek literature on the issue of chrysoprase is the book of Theophrastus of Eresos (c. 372-282 BC) “
Since the times of Pliny the Elder (23-79 AD), the knowledge of this stone has been supplemented by new data about its physical (including optical) properties, origin, etc. (see e.g. Gliozzo 2019). In 1652, the first book in English:
A very significant progress in the knowledge of chrysoprase was made by the Swedish chemist Johan Gottschalk Wallerius (1709-1785). In
The last decades of the 18th century were a breakthrough in knowledge about chrysoprase. Its chemical composition was finally determined and it was definitely included into the group of SiO2 minerals. The knowledge about its Silesian origin became common. The green coloration of chrysoprase caused by nickel compounds was first discovered by the German apothecary Martin Heinrich Klaproth (1743-1817), called the “father of analytical chemistry”. He was followed by another German mineralogist and chemist Friedrich August Cartheuser (1734-1796) as well as by the French mineralogist and chemist Balthasar-Georges Sage (1740-1824). Both scientists incorporated chrysoprase (
The systematics of chrysoprase most similar to the currently accepted was provided by Johann Friedrich Gmelin (1748-1804) in the academic textbook
A new classification system, based on the theory of A.G. Werner, was presented by the German mineralogist Dietrich Ludwig Gustav Karsten (1768-1810) in his academic textbook
Two well-known persons close the review of chrysoprase literature at the time: Abraham Gottlob Werner (1749-1817) and Johann Gottfried Schmeisser (1767-1837). A.G. Werner, a German scientist known as the “father of geology”, created a canon for identifying and classifying minerals based on their external characteristics. He first presented these concepts in the book
Ultimately, at the end of the 18th century, European mineralogists accepted without any reservations that chrysoprase is a variety of chalcedony colored with nickel and they also knew its Silesian origin.
The name of chrysoprase is related to its color shades, which are a mixture of yellow and green (Greek Opal A (amorphous) – opal CT (cristobalite-tridymite) series; Opal CT – chalcedony series; Chalcedony – opal CT series; Chalcedony series; Chalcedony – moganite – quartz series.
All these silica phases are found in chrysoprase, but in various proportions. Due to such a complex mineral composition of chrysoprase, its hardness should be replaced by the grading resistance (GR) parameter, as proposed by Hänni et al. (2021).
Chrysoprase shows varying degree of green color saturation (from light to dark green) (Fig. 1). After the years of research, it was found that the color of this stone is related to the dispersed nickel-bearing minerals of “kerolite-pimelite” series (Sachanbiński 1985; Heflik et al. 1989; Natkaniec-Nowak et al. 1989; Nagase et al. 1997; Sachanbiński et al. 2001; Sojka et al. 2004; Witkowski, Żabiński 2004; Čermakova et. al. 2017). In addition, the color of chrysoprase is also influenced by willemseite of the pyrophyllitetalc group (Vasconcelos, Singh 1996) and gaspéite – a nickel-rich variety of calcite (Henn, Milisenda 1997; Graetsch 2011). It turns out, however, that the concentrations of NiO in chrysoprase vary in particular deposits around the world: the highest contents (5.631 wt.%) were found in Australian chrysoprase (Jiang et al., 2021) whereas the lowest values (0.004-1.23 wt.%) were encountered in Polish stones from Szklary near Ząbkowice Śląskie, in Lower Silesia (Figs 1, 2). Comprehensive studies of Australian chrysoprase using many modern analytical methods, including transmission electron microscopy (TEM), X-ray fluorescence (XRF), UV-Vis spectroscopy, Raman spectroscopy (FT-RS) and colorimetric analysis showed that, in addition to nickel, the brightness and the shades of green color of these stones are influenced by the sum of chromium and iron. Chrysoprases with a low degree of crystallinity contain more Ni and their green color is more intense (Jiang, Guo 2021; Jiang et al. 2021). Moreover, it was found that the green color in chrysoprase appears already at the content of only about 0.05 wt.% NiO (Ostrowicki 1965). Interestingly, apart from nickel and the aforementioned chromium and iron, many other trace elements (e.g. Sr, Ba, Ag, As, Be, Co, Cu, Pb and others) and rare earths (e.g. Ce, Nd, Sm, Eu, Tb, Tm, Yb, Lu) may also be present in chrysoprases. This is indicated by the results of study on emerald-green chrysoprase from Haneti-Itiso (Tanzania) provided by Kinnunen and Malisa (1990).
Different color varieties of chrysoprase from Lower Silesia (Poland): A – opal chrysoprase (prazopal), Szklary; B – light green chrysoprase, Szklary; C – matrix chrysoprase, Wiry; D – botryoidal chrysoprase, Szklary; E – matrix chrysoprase, Szklary; F – chalcedony chrysoprase, Szklary. Photos by P. Rachwał.
Chrysoprase from selected occurrences in the world: A – Australia. Photo by J. St. John, 2018, Wikimedia Commons; Creative Commons Attribution-Share Alike 4.0 International license; B – Tanzanian emerald green chrysoprase. Collection of the Mineralogical Museum of the University of Wrocław. Photo by P. Piotr Rachwał; C – Sarykul-Boldy, Kazakhstan. Collection of the Fersman Mineralogical Museum of Fersman in Moscow; D – Neolithic chrysoprase blade, Suhaila, Ras al Khaimah Emirate. Photo by V. Charpentier; E – The oldest specimen of chrysoprase from Braszowice, Lower Silesia, found in 1869. Mineralogical Museum of the University of Wrocław. Photo by P. Rachwał.
Jiang et al. (2021) conducted a color assessment of the analyzed Australian chrysoprases using the Munsel N9.5 background and fluorescent lamp (correlated color temperature of 6,504K) and a special affinity propagation (AP) clustering algorithm for processing the obtained measurement results. By determining the noticeable differences in the color of individual samples and the cluster centers (AP) they classified the chrysoprase colors into the five groups: Fancy Light, Fancy, Fancy Intense, Fancy Deep and Fancy Dark. Moreover, Jiang et al. (2021) proposed the application of this classification method also to other green stones, e.g. emerald, jade and tourmaline.
Chrysoprase is also translucent to various degrees, as is chalcedony, which explains why it has been classified for many years as a colorful variety of this mineral. The lack of transparency of chrysoprase is due to its microporosity (pore diameters from 0.03 to 10 μm), observed in SEM images, as well as to the presence of H2O particles located in the internal defects (Jiang et al. 2021).
Chrysoprases derived from various deposits around the world reveal a wealth of mineral, structural and genetic varieties (Fig. 2). In weathering crusts developed on ultramafic rocks, chrysoprases were formed as a result of transformation of silica gel into minerals from the SiO2 group. As previously mentioned, individual SiO2 polymorphs are present in different proportions in chrysoprases and interpenetrate themselves. Moreover, these show very diverse microstructural forms, e.g. fibrous, radial-fibrous, spherulitic (globular), checkerboard-like, mosaic, rosette and mixed (Sachanbiński 1985). Such variable microstructural forms are accompanied by a diversity of habits and sizes of mineral individuals. Detailed recognition of the internal structure of chrysoprases requires the application of comprehensive mineralogical tests (e.g. PXRD, FT-IR, FT-RS – see Sachanbiński et al. 2001), mainly in order to find out the degree of crystallinity of individual components from the SiO2 group (Plusnina, Szpila 1990; Gaweł et al. 1997). This allows us to distinguish a number of different structural varieties of chrysoprase, ranging from chalcedony chrysoprase to opal chrysoprase, called
From the gemological point of view, purity plays an important role in the qualitative assessment of any raw material, which considers both the quantity and the quality of mineral and organic intergrowths, and various types of internal defects (e.g. microcracks, pores, etc.). In the case of chrysoprase, the studies reported on various types of fluid inclusions, usually single and/or two-phase, syn- and epigenetic, and hosting solid, liquid, and/or gaseous phases (Kozłowski, Sachanbiński 1984). Predominant are mineral intergrowths, which play an important role in genetic considerations, being a specific proof of the environment of chrysoprase formation and the subsequent processes of their transformations. The most important are clay minerals mentioned above, which influence the color of chrysoprase. In turn, liquid and gas inclusions play a crucial role in thermobarometric tests, because on their basis the temperature of mineralizing processes can be determined. Studies of fluid inclusions together with stable isotope analyzes, especially for δ18O, have shown that chrysoprases could also be formed with the participation of hydrothermal solutions (Miljević et al. 1994; Skrzypek et al. 2003; Hatipoğlu, İlbeyli 2015).
As mentioned above, chrysoprase is genetically related to ultramafic rocks (peridotites, dunites) and transformed members of ophiolite complexes (serpentinites), where it forms interesting color varieties with opal (
Map of chrysoprase occurrences in the world. Prepared by M. Sachanbiński.
The chrysoprase market has changed over the centuries, along with the discovery of more and more accumulations, the growing demand from craft workshops, the fashion trends, etc. A special advantage of this stone was and still is its color, which is alleged to have a positive effect on humans associated with the joy of life and the hope for a better future (alike the blue color). In color therapy, green is supposed to trigger positive emotions in human’s mind, to soothe and to facilitate the relax. Homogeneous, intense, grass-green (emerald-green) or bluish-green shades of chrysoprase (
Currently, chrysoprase is a green stone of high decorative value, sought after on the jewelry market. Both the raw specimens and the cabochons are valued, the latter especially when crafted from pure, homogenous rawmaterial. Commonly, chrysoprase is also used to make various fancy forms, e.g. pears (
Chrysoprase was already used in the decorative arts of ancient Rome and medieval Europe (Sachanbiński 1980; Evangelista et al. 1992). Many chrysoprase artifacts discovered over the years during archaeological works are now in world museum collections as well as in the hands of private lovers and collectors of stones (Figs 2, 4). The ennoblement for the Silesian chrysoprase is placing it in the royal crown – a masterpiece of medieval goldsmithing, found in 1985, in so-called “treasure from Środa Śląska” (Poland) (e.g. Girulski, Sachanbiński 2018). Chrysoprase is used also as a luxury cladding and inlay stone in ebenistics, in Florentine (
Chrysoprase in the world of art: A – element of the frame (left side) of the icon
Each stone was associated with esoteric symbolism, often read on the pages of the Bible and, according to some scientists, also in the Torah. In the Septuagint, the first translation of the Old Testament, chrysoprase did not appear, although some experts found it in the prophecy of Ezechiel (27:16), as the
In this article, the authors often questioned the current classification of chrysoprase, in which this stone is still categorized as a color variety of chalcedony. However, the analytical data clearly shows that chrysoprase is not a mineral. Instead, it is an example of complex silica assemblage, in which the percentage of individual SiO2 polymorphs determines its internal and external characteristics. Therefore, it seems necessary to modify the existing taxonomy and mineralogical-petrographic systematics of chrysoprase. Broda et al. (2022) described the larimar from Dominican Republic, which is an example of complex pectolite mineralization and provided also an example of agate which, alike chrysoprase, is composed of variable proportions of SiO2 phases (see e.g. Dumańska-Słowik et al. 2008, 2013; Natkaniec-Nowak et al. 2016). Sometimes, SiO2 polymorphs can generate unique optical properties of agates, previously attributed only to precious opal (Natkaniec-Nowak 2020). Moreover, Broda et al. (2022) used for the first time the term “polyminerals” to describe this type of complex mineral compounds. Thus, the authors intend to start a discussion among mineralogists and petrologists, not treating this term in an unambiguously binding manner, but rather as a proposal for the future nomenclature of many similar mineral compounds showing a complex internal structure.