— Unveiling the Stories Behind Two New Minerals: “Empty Zinc-Ag-Antimonite” and “Empty Iron-Ag-Antimonite”

　 　◎ Reporter Liu Xuan from this newspaper

　 　Core Reading:

　　Following the publication of the new mineral “empty-zinc argentopyrite,” it has attracted widespread attention and sparked intense debate among mineralogists on internationally recognized mineralogical websites. Some argue that the origin of empty argentopyrite remains an unsolved mystery within the argentopyrite group, while others speculate that its unique structure may be linked to a specific Ag/Cu ratio in hydrothermal fluids during mineral formation. Based on this hypothesis, an excessive silver content in hydrothermal fluids might actually hinder the formation of vacancies in argentopyrite... In 2021, the research team led by Qu Kai from the Tianjin Geological Survey Center of the China Geological Survey once again discovered a new mineral—the empty-iron argentopyrite—in the Yindongpo deposit. This groundbreaking discovery directly refutes the aforementioned academic conjecture.

　　The “Top Ten Geological Achievements of Henan Province” were recently announced, and among them, “The Discovery and Naming of Two New Minerals in Nature in Henan” has drawn widespread attention from all sectors of society. The two newly discovered minerals—“empty zinc-silver tennantite” and “empty iron-silver tennantite”—were identified and named by the research team led by Qu Kai, a senior engineer at the Tianjin Geological Survey Center of the China Geological Survey. The discovery of these two new minerals not only expands the diversity of minerals found in nature and enhances China’s international standing in mineralogy, but also provides new insights and references for understanding and utilizing natural minerals.

　　How were the two new minerals discovered? What is the significance of their discovery in the field of mineralogical research? What potential does China have in the area of discovering new minerals? To address these questions, a reporter from the China Mining News recently interviewed Qu Kai.

　　 Discovery: Two New Minerals Named

　　Research on new minerals is an important foundational endeavor in the field of Earth sciences. The discovery and naming of new minerals represent original achievements—“from zero to one”—and enjoy the highest prestige in the international mineralogical research community. They serve as a key indicator of a country’s level of mineralogical research. As of March 2022, a total of 5,794 new minerals had been discovered worldwide.

　　The two new minerals—“empty zinc-silver chalcocite” and “empty iron-silver chalcantite”—were both discovered at the Yindongpo gold mine in Tongbai County, Nanyang City, Henan Province. The related research was jointly conducted by the Tianjin Center of the China Geological Survey, together with six other domestic research institutions, including the Third Institute of Geology and Mineral Resources of Henan Province. In 2020, Qu Kai’s research team carried out a study on the occurrence states of elements at Yindongpo in Henan. “This work was initiated in early 2020. Due to the impact of the COVID-19 pandemic, field samples were not obtained until the end of June of the same year. After two months of sample processing and microscopic identification, we preliminarily identified the target new mineral on August 25,” Qu Kai told reporters during an interview, describing the discovery process of “empty zinc-silver chalcocite.” During the research, the team found a chalcocite specimen with a unique chemical composition. Following systematic mineralogical studies—including physical properties, chemical composition, crystal structure, and spectroscopic characteristics—the team confirmed that this specimen represented a previously unknown mineral belonging to the chalcocite group. This new mineral lacks one divalent anion compared to typical zinc-silver chalcocite. It maintains overall charge balance through the presence of a special [Ag6]4+ structural unit. Because of the structural vacancies present in its lattice, it was named “empty zinc-silver chalcocite.” On September 24 of the same year, the research team formally submitted an application for the new mineral to the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association. In January 2021, the mineral was unanimously approved by the Commission and officially recognized.

　　Following the publication of the new mineral “empty zinc argentopyrite,” it has attracted widespread attention and sparked intense debate among mineralogists on an internationally recognized mineralogical website. Some believe that the origin of empty argentopyrite remains an unsolved mystery within the argentopyrite group; others speculate that its unique structure may be linked to a specific Ag/Cu ratio in the hydrothermal fluids during mineral formation. Based on this hypothesis, an excessive silver content in hydrothermal fluids might actually hinder the formation of vacancies in argentopyrite... In 2021, Qu Kai’s research team once again discovered a new mineral—empty iron argentopyrite—in the Yindongpo deposit. This groundbreaking discovery directly refuted the aforementioned academic speculation. In April 2022, “empty iron argentopyrite” was officially approved by the New Mineral Nomenclature and Classification Committee of the International Mineralogical Association. Currently, the holotype specimen of the new mineral is housed in the Geological Museum of China. “However, to pinpoint exactly which physicochemical conditions at Yindongpo gave rise to this new mineral, we will focus our next-stage research efforts,” said Qu Kai.

　　 Research and explore the social value of new minerals.

　　The discovery of new minerals can enrich the variety of minerals found in nature and also provide a scientific basis for humanity to better understand and utilize new substances in the natural world.

　　Qu Kai told reporters that the chalcocite group, as an “ancient” mineral family, is commonly found in various types of hydrothermal ore deposits. Due to the substitution of isovalent or heterovalent elements at multiple crystallographic sites, this group is considered the most complex sulfosalt mineral family. As a common mineral in hydrothermal deposits, chalcocite possesses significant economic value. Moreover, its silver content serves as an indicator parameter for ore-forming temperature, making it highly important for ore deposit studies. Both “zinc-deficient argentochalcite” and “iron-deficient argentochalcite” are members of the chalcocite group, with their key characteristics including: the mineral appearing grayish-black in hand specimens, grayish in reflected light with a slight greenish-gray tint, and exhibiting brownish-red internal reflections; possessing an opaque metallic luster and black streak; being brittle with conchoidal or irregular fractures; and occurring closely associated with minerals such as zinc chalcocite, spiriferous argentite, argentite-sulfide, sphalerite, galena, pyrite, chalcopyrite, and quartz. In terms of properties, zinc-deficient argentochalcite, thanks to its unique and distinctive structure, demonstrates outstanding performance in catalysis, chemical sensing, and optoelectronic functional materials. Furthermore, its formation mechanism can provide new insights and references for the field of synthetic materials. On the other hand, iron-deficient argentochalcite is the silver-richdest mineral within the chalcocite group found in nature, with a silver content reaching as high as 52.3%. Its silver content serves as an indicator parameter for ore-forming temperature, making it of great significance for studying the genesis of ore deposits.

　　Qu Kai further explained that minerals, as fundamental building blocks of the Earth system and one of its environmental components, have always been an essential material basis for human survival and development. However, among the more than 6,000 naturally occurring minerals currently known, only a little over a hundred have had their structures and properties relatively well understood and widely applied. In recent years, with the continuous discovery of new minerals and the ongoing unveiling of their novel properties, multidisciplinary fields—including earth sciences and materials science—have achieved remarkable breakthroughs in the study of mineral resources and functional materials. There’s a saying circulating online: “When you’re at a loss, turn to graphene; when all else fails, reach for perovskite—a panacea.” In 1839, German mineralogist Gustav Rose, while exploring the Ural Mountains, discovered a mineral whose elemental composition was CaT. _I O ₃ This mineral was subsequently named “perovskite” (Chinese translation: kaitaiqi). Today, materials derived from this mineral—with its general structural formula of ABX3—have become the hottest “star” in the field of new energy materials. Meanwhile, “graphene,” which was awarded the 2010 Nobel Prize in Physics for its discovery through exfoliation of graphite, has long been a household name.

　　As new minerals continue to be discovered and new mineral properties are increasingly revealed, not only will this enrich the variety of mineral resources needed for high-quality economic and social development and facilitate breakthroughs in mineral exploration, but it will also make a significant contribution to achieving efficient and clean resource utilization.

　　It is reported that the research team led by Qu Kai has discovered a new mineral—hollow zinc-silver chalcocite. Although the unique [Ag6]4+ structural motif found in this new mineral has so far been observed only in three natural minerals, including the newly identified one, it has already been documented in synthetic materials and has demonstrated remarkable performance in catalysis, chemical sensing, and optoelectronic functional materials. Chalcocite is a relatively abundant group of naturally occurring minerals on Earth, composed primarily of environmentally friendly elements such as copper and sulfur. Each unit cell of chalcocite features a complex crystal structure with a large number of atoms, which contributes to its low thermal conductivity. Moreover, thanks to its highly symmetric crystal structure, chalcocite exhibits high band degeneracy, which helps enhance the power factor. Currently, in the field of synthetic material fabrication, chalcocite—especially those rich in nickel—are being considered as promising candidates for large-scale thermoelectric applications. Therefore, the novel mineral with its distinctive structural characteristics recently discovered by Qu Kai’s research team in nature offers valuable insights into the crystal chemistry and formation mechanisms of these minerals, providing a fresh reference for the development of synthetic materials.

　　 Focus on and continuously strengthen research into new minerals related to critical metal ores.

　　In 1958, China discovered its first new mineral—“Xianghuashi.” Over the past 64 years, China has identified a total of 162 new minerals in nature (including 21 discovered by foreign research teams), ranking eighth worldwide in total number. On average, China discovers 2.5 new minerals each year. “Given China’s vast territory and abundant mineral resources, from this perspective, China still has great potential in the field of new mineral discovery,” said Qu Kai.

　　It is understood that the mineral research team at the Tianjin Geological Survey Center of the China Geological Survey primarily engages in fundamental geological surveys and genetic mineralogical studies related to critical minerals. The team focuses particularly on investigating the occurrence states and enrichment mechanisms of key metals, as well as discovering and studying new minerals. Since 2019, the Tianjin Geological Survey Center of the China Geological Survey has spearheaded the discovery of five new minerals in nature and participated in the discovery of four additional new minerals—five of which belong to the chalcocite group, and four of which are rare or rare-earth element minerals associated with critical minerals. In addition, systematic mineralogical research is currently underway on several potential new minerals containing rare and dispersed elements and rare-earth elements.

　　In the next phase, what work will the research team focused on new minerals undertake? Qu Kai stated that the team plans to concentrate on the following three areas in the next step: First, closely monitor and master new theories and technologies in the field of mineralogy, continue strengthening research on new minerals and their formation mechanisms related to critical metal resources, and actively participate in the International Mineralogical Association’s efforts to develop classifications and rules for mineral groups, thereby enhancing China’s international influence in the field of new mineral research. Second, focus on the deep Earth and deep space, exploring from a mineralogical perspective the mysteries of Earth’s internal structure as well as the formation and evolution of terrestrial planets in the inner solar system. Third, fully leverage the advantages of the China Geological Survey’s physical geological data resources, collaborate with relevant institutions to carry out basic geological surveys aimed at identifying potential new minerals in China, deeply tap into the potential of existing precious specimens, promote the secondary utilization and development of physical geological data, and bring more new minerals to light on our nation’s land.