Rocks under the Microscope Zone II Versions EN1 Vol 5 (3) 2020
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A photomicrograph dataset of rocks for petrology teaching at Nanjing University
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Abstract & Keywords
Abstract: Thin sections have played an irreplaceable role in the nearly 100-year history of petrology teaching and research in the School of Earth Sciences and Engineering, Nanjing University. Despite their depletion, loss, supplementation, and update, the thin sections at Nanjing University have formed a relatively comprehensive set, which includes 28 types of sedimentary rock, 40 types of igneous rock, and 40 types of metamorphic rock. As a whole, they cover over 90% of common rock types and contain more than 95% of the common minerals and rock textures mandated by the geology syllabus. This dataset results from a collective endeavor to electronically informatize the thin sections currently used by Nanjing University for petrology teaching. It includes a total of 2,634 polarized-light photomicrographs of 324 thin sections of 108 types of rock. To facilitate the sharing of petrology teaching materials, we present the photomicrographs and information tables of these thin sections here. This dataset can be used by instructors as teaching materials or by students for professional training and self-learning. Of high quality and a uniform standard, these image data can be used for research on machine learning and rock identification through artificial intelligence. These photomicrographs can also be used as materials for advertising and pattern design in production practice.
Keywords: thin section; polarized photomicrograph; sedimentary rocks; igneous rocks; metamorphicrocks ; petrology; Nan; ng Univer; ty
Dataset Profile
TitleA photomicrograph dataset of rocks for petrology teaching at Nanjing University
Data corresponding authorHu Xiumian (huxm@nju.edu.cn)
Data authorsLai Wen, Jiang Jingxin, Qiu Jiansheng, Yu Jinhai, Hu Xiumian
Time rangeThe rock samples were collected during 1970s to 2010s. The polarized photomicrographs of the thin sections were taken in 2014 and 2019.
Geographical scopeChina.
Polarized microscope resolution1280*1024 or 4908*3264 pixels
Data volume4.94 GB
Data format*.jpg, *.xls
Data service system<http://dx.doi.org/10.11922/sciencedb.j00001.00097>
Source of fundingNational Key R&D Program of China (2018YFE0204201)
Dataset compositionThe dataset includes six data files, which are: “Photomicrographs of sedimentary rocks for Nanjing University teaching.zip,” “Photomicrographs of igneous rocks for Nanjing University teaching.zip,” “Photomicrographs of metamorphic rocks for Nanjing University teaching.zip,” “Information table of sedimentary rocks for Nanjing University teaching.xls,” “Information table of igneous rocks for Nanjing University teaching.xls,” and “Information table of metamorphic rocks for Nanjing University teaching.xls.” Among them, the three photomicrograph files stores 2634 polarized photomicrographs (*.jpg) of rock thin sections, with a data volume of 4.94 GB, while the three information tables records the identification data of the rock thin sections, with a data volume of 99.1 KB.
1.   Introduction
The origins of the petrology major of the School of Earth Sciences and Engineering, Nanjing University, can be traced back to the fall of 1921, when Zhu Kezhen created Nanjing University’s Department of Geoscience. At that time, the department added new courses on geology and meteorology, teaching courses such as petrology and mineralogy, and began to systematically collect and purchase various rock and mineral specimens [1]. The Department of Geoscience of the National Central University had established petrology and rock thin-section laboratories in the 1920s, equipped with instruments such as microscopes and thin sectioners, and was in possession of over 800 kinds of rock sample and 280 kinds of thin section [2]. In 1930, the geology major separated from Nanjing University’s Department of Geoscience and became an independent department. Subsequently, with the support of school funding and policies, through field collection, global procurement, and other means, the Department of Geology collected more than 10,000 specimens, including more than 2,000 rock specimens, which had been collected from Europe, the United States, and elsewhere in the nineteenth century, and which are now preserved in the Rock and Mineral Department of the School of Earth Science and Engineering, Nanjing University. These rock specimens from Germany, France, the United States, Japan, China, and other parts of the world constitute more than 300 rock types and more than 900 thin sections for teaching [2]. However, after the War of Resistance Against Japan (also known as Second Sino–Japanese War) and the Cultural Revolution, many rock specimens and thin sections disappeared from the collection. In addition, thin sections were frequently lost due to their fragility and their use in the teaching process.
Having re-screened the typical rock specimens from China, teachers and students produced three types of thin section for teaching, and in the subsequent process of teaching, updating, and curriculum reform, the current collection of typical and representative thin sections was created by constantly increasing, and replacing samples. In order to protect the collection and to better preserve the information contained in these thin sections, conducting an electronic informatization of these standard teaching thin sections to securely store the photomicrographs (micrographs) and other data is essential.
As different thin sections are used in different schools, there is little communication and sharing of these teaching materials between geoscientific colleagues. Geoscience professionals from different schools often have different ideas about the same concept (e.g., on feldspar or quartz sandstone [3]); therefore, if the online sharing of teaching materials such as these rock thin sections can be realized, it will help to eliminate these conceptual differences and promote a full exchange and discussion among geology peers. In addition, online teaching materials are urgently needed to meet the needs of the rapid growth and popularity of online teaching in response to the current COVID-19 pandemic. The online sharing of materials, such as the microscopic images of these thin sections, will also facilitate students’ online self-learning.
Based on the above, this dataset aims to organize the microimage data and sample information system on sedimentary, metamorphic, and igneous rock thin sections for teaching in the Rock and Mineral Department, School of Earth Sciences and Engineering, Nanjing University, and to share this data with interested peers online.
2.   Data collection and processing
The teaching thin sections from the Rock Mining Teaching and Research Department of the School of Earth Science and Engineering at Nanjing University have been selected from the large number of rock samples that have been studied by frontline researchers. Therefore, these thin sections have typical characteristics in terms of rock composition and structure and are highly representative of various types of rock. For example, the granite thin sections from the 1980s are representative samples selected from thousands of rock thin-section identification data from the South China Granite Research Project [4]. Thin sections from before 2000 were polished by the faculty members of Nanjing University’s Rock and Mineral Department to ensure that they met the standard thickness of 0.03 mm. The newest thin sections from this century have been produced by a professional rock sheeting company.
In order that these thin sections can be better viewed from all angles, a single-polarized and a cross-polarized photo of each thin section has been taken at 0° after selecting a representative field of view, and then one photo has been taken every 15° of rotation under cross polarization. If advanced white interference-colored minerals, such as calcite, are encountered, the thin slice is inserted into a gypsum test plate of λ wavelength at 90° and one micrograph is taken. Each thin slice has one single-polarized photo and seven or eight cross-polarized photos, as shown in Figure 1. Other photographic techniques have been used to standardize rock micrographs to meet photographic requirements [5], and then the sedimentary, igneous, and metamorphic rocks, along with the other three major categories of rock teaching sheet, were randomly selected from boxes for standardized photos. Each micrograph has been named according to the following format: "thin section location" + "rock name" + "thin section box number" + "the digital number of the camera field of view,” e.g., "Sedimentary 8 feldspatho-quartzose sandstone 2–5" represents the fifth micrograph of sedimentary rock no. 8, which is the second feldspatho-quartzose sandstone thin section.


Figure 1   Single-polarized (-) and cross-polarized (+) micrographs of the “Igneous 15 trachyte 1” sample
The information collection method for each thin section was uniformly executed according to the "Rocks under the Microscope" standard, in which the composition, structure, tectonics, and other details of the thin section are systematically described in tabular form, and from which the relevant geographic and other information related to the thin section was also obtained. This includes the description and designation of sedimentary rock thin sections [5]. Details of the carbonate rocks, evaporites, sedimentary minerals, and other endogenous sedimentary rocks have been completed with reference to the limestone table and details of the volcanic clastic rock and land-based clastic rock with reference to the clastic rock table.
Given the absence of tables to complete image information on metamorphic and igneous rocks, this study used those relating to clastic rocks and limestone and the design principles developed by "Rocks under the Microscope" [5] as the model to design Tables 1 and 2, respectively, for these images.
Table 1   Identification information for igneous rock thin sections
No.Thin section IDRock typeaccurate namingPhotomicrograph numberType and content of dominant or porphyritic mineralsAccessory mineralsType and content of matrixTexture of igneous rockStructureMagmatismOthers
Diameter (mm) and sizerelative sizeDegree of crystallizationDegree of self-shapeShapeInter-particle relationship
1Igneous 1 lherzolite 1ultramafic rockslherzolite(1)*Olivine 65%, augite 20%, hypersthene 14%Spinel 1%0.5–3 mm, mid-grainequigranularFull crystallineHolocrystalline to HypocrystallineGranular and short columnarintrusive action
Note: (1)*refer to Photomicrograph numberIgneous 1 lherzolite 1-1, Igneous 1 lherzolite 1-2, Igneous 1 lherzolite 1-3, Igneous 1 lherzolite 1-4, Igneous 1 lherzolite 1-5, Igneous 1 lherzolite 1-6, Igneous 1 lherzolite 1-7, Igneous 1 lherzolite 1-8. The orange header is required information; the blue header is optional information according to the actual needs
Table 2   Identification information for the metamorphic rock thin sections
No.Thin section IDRock typeaccurate namingPhotomicrograph numberType and content of ordinary mineralsmetamorphic mineralsType and content of matrixRelict textureMetamorphic textureAlternate texturedeformation and cataclasis textureStructureMetamorphismOthers
Diameter (mm) and sizerelative sizeInter-particle relationshipShape
1Metamorphic 1 Mylonite 1MyloniteMyloniteMetamorphic 1 Mylonite 1-1Quartz 30%, plagioclase 55%, potash feldspar 5%, biotite 10%Fine-grained metamorphic crystal in fragments (0.5-1.5mm), microscopic metamorphic structure of matrix(<0.1mm)Unequal graingranularWavy extinction, sub-grain, silk ribbon structure, mylonite structure, knee foldGneissic structure or eyeball structureDynamic metamorphism
Note: (1)*refer to Metamorphic 1 Mylonite 1-1, Metamorphic 1 Mylonite 1-2, Metamorphic 1 Mylonite 1-3, Metamorphic 1 Mylonite 1-4, Metamorphic 1 Mylonite 1-5, Metamorphic 1 Mylonite 1-6, Metamorphic 1 Mylonite 1-7, Metamorphic 1 Mylonite 1-8. The orange header is required information; the blue header is optional according to the actual needs.
The igneous "rock types" set out in Table 1 are classified into ultrabasic or ultramafic rocks, and basic, intermediate, acidic, alkali, and other related rocks based on criteria such as the rock’s SiO2 content and the degree of alkali saturation. There are a few rocks related to alkaline rocks, such as carbonatite [6] (Figure 2). For the further accurate naming of igneous rocks, the following rules need to be followed [6]: (1) The basic names of igneous rocks are obtained graphically by QAPF classification (i.e., classification by the relative content of four minerals: quartz, alkaline feldspar, oblique feldspar, and pseudofeldspar) from the mineral content obtained from statistical or chemical composition calculations; (2) Further names are formed by prefixing the names of minor minerals with content ≥5%. If there are multiple minor minerals to be included in the naming, the higher the content, the closer to the basic name of the rock; (3) For shallow igneous intrusive rocks with a microcrystalline or fine-grained structure, "microcrystalline" is prefixed before the name of the corresponding composition of the shallow igneous intrusive rock, such as microcrystalline diorite; if porphyritic in structure, "porphyry" is added after the corresponding shallow igneous intrusive rock as a suffix, e.g., granite porphyry or monzonitic porphyry; (4) On the physical characteristics of ultrashallow orogenic intrusive rocks formed from ejecta, because they are mostly porphyritic in structure, "porphyry" can be used with the name of the lava, e.g., andesite porphyry; if the ultrashallow orogenic rocks belong to the subvolcanic phase, "sub" is added to the name as a prefix, e.g., sub-rhyolite porphyry; (5) For deep or ejected rocks with porphyritic structures, the structure is generally not included in the name to avoid confusion with shallow porphyritic rocks.


Figure 2   Common types of igneous rocks: a classification reference. Those in orange can be observed in this dataset [6]
The type and content of the rock-forming minerals can be observed in the igneous micrographs, with occasional minor minerals (e.g., zircon, spinel, apatite, etc.) of <1%. Table 1 in this dataset refers to the percentage of the visual area of the micrographs of various types of mineral in the representative field of view. The texture of igneous rocks refers to the degree of crystallinity and the size, shape, and interrelationships of the constituent rock materials, including minerals [6]. The information on texture includes descriptions of six categories relating to minerals: absolute size, relative size, shape, degree of crystallization, degree of self-shape, and interrelationships between particles (Figure 3). The structure of the igneous rocks relates to the relationship between the parts that make up the rock in terms of their inter-arrangement, configuration, and filling patterns [6], which are mainly macroscopically visible. Thin sections usually also show structures such as rhyolite, mottled, pearl, stomatal, and almond structures (Figure 3).


Figure 3   Common texture and structures in igneous rocks: a classification reference.
Descriptors in orange are the types of texture or structure that can be observed in this dataset [6]
The magmatic action of igneous rocks is mainly classified into intrusive action and volcanic action by petrographic characteristics. Advanced study should be based on the data relating to igneous rock composition, texture, and structure to further determine whether the rock was formed by crystallization differentiation, assimilation and mixing, magma mixing, or magma liquid unmixing [6].
The classification of metamorphic rocks is mainly based on the metamorphic structure and mineral composition of these rocks, and there are about 20 common basic types of metamorphic rock, including slate, chondrite, schist, gneiss, migmatite, chyllite, hornblende, metamorphic granite, oblique hornblende, mafic rock, granite, marble, quartzite, skarn, cataclasite, dacite, and serpentine [7] (Figure 4).


Figure 4   Common types of metamorphic rocks: classification reference.
Names in orange are included in this dataset [7]
The following rules apply to the accurate naming of metamorphic rocks [7]: (1) “Characteristic metamorphic minerals” + “common metamorphic minerals” + “basic name,” e.g., staurolite–biotite schist; (2) When multiple minerals are included in the name, those with less of the same mineral content are ranked first and those with more are ranked second; (3) Ordinary minerals ≥5% are named, and characteristic metamorphic minerals are named regardless of their content; (4) When multiple minerals are present, the first two words are usually taken to simplify the mineral nomenclature in Chinese, such as staurolite–garnet–biotite–quartz schist; (5) With gneiss, the feldspar type is added before the basic name, such as amphibolite–plagioclase gneiss and garnet–sillimanite–potassium gneiss; (6) Some structural features are added before the name, such as banded migmatite and spotted hornblende; (7) If the rocks are slightly metamorphic, they are named as "metamorphic” + “original rock name,” such as metamorphic phyllite and metamorphic siltstone; (8) If the rocks are superimposed metamorphic rocks or hydrothermally altered rocks, they are named with "XXX” + “original rock name,” such as chyllonitic amphibolite, chloritic dolomite schist, and hornblende siltstone.
The minerals in the metamorphic rocks include ordinary minerals and metamorphic minerals (Table 2). The types of mineral need to be described systematically with the estimated area percentages shown in the micrographs, as set out in Table 2. Ordinary minerals in metamorphic rocks refer to mineral types that are also common in sedimentary and igneous rocks, such as quartz, muscovite, biotite, plagioclase, potash feldspar (or alkaline feldspar), calcite, dolomite, and amphibole. There are dozens of metamorphic minerals, which include sericite, serpentine, garnet, sillimanite, kyanite, and jadeite, all of which are formed under different metamorphic conditions (Table 3). The texture of metamorphic rock is mainly observed under a microscope in thin section, including metamorphic, relict, metasomatic, fragmentation, and deformation textures (Table 2). More than 40 common textures can be observed in thin section (Figure 5). Although most macroscopic metamorphic rock structures are impermeable, plate, plaque, schistose, gneiss, mixed, strip, augen, and other structures (Figure 5) can also be observed in thin section.
Table 3   Metamorphic minerals of different composition and formed in different environments (modified from [7])
Mudstone (Al-rich) seriesFeldspar-quartz seriesSilica (silicon rich) seriesCarbonate seriesBasic (Fe-Mg rich) seriesSuperferrous magnesium series
Non- metamorphicQuartz, Muscovite, Biotite, PlagioclaseQuartz, plagioclase, potassium feldspar, biotiteQuartz, micaCalcite, dolomite, quartzPlagioclase, amphibole, chlorite
Low-grade metamorphismSericite, chlorite, pyrophyllite, chloritoid, tourmaline, manganese-rich garnetSericite, muscoviteSericite, Muscovite, MagnetiteSerpentine, talc, zoisite – epidoteChlorite, epidote, actinolite, acid plagioclase, zeolite, prehnite, biotite, pumpellyiteSerpentine, talc, chlorite
Middle-grade metamorphismAndalusite, Almandine, Staurolite, KyaniteAndalusite, Almandine, KyaniteAndalusite, Almandine, Kyanite, AmphiboleTremolite, fushanite, garnet, garnetamphibole, neutral plagioclase, anthophyllite,
cummingtonite
Anthophyllite, tremolite, phlogopite
High-grade metamorphismSillimanite, cordierite, fake sapphire, corundumSillimanite, orthoclaseSillimanite,hyperstheneWollastonite, diopside, periclase, periclase, wollastonite, forsteriteClinopyroxene, orthopyroxene, almandite-pyrope, perthite, spinelClinopyroxene, orthopyroxene, olivine, chromium spinel
High-pressure metamorphismphengite, sodium mica, talc + kyanite, zoisite + kyanitephengite, Paragonite, lawsonite, jadeitephengite, jadeite, TopaaragoniteGlaucophane, lawsonite, jadeite, omphacite., pyrop, Stilpnomelanepyrop, talc


Figure 5   Common texture and structures in metamorphic rocks: classification reference.
Orange labels refer to the types of texture or structure observed in this dataset [7]
The type of metamorphism that formed the metamorphic rocks also requires comprehensive judgment in terms of the composition, texture, structure, and other thin-section features, as well as other information such as temperature and pressure conditions and geological background. Types of metamorphism include regional, dynamic, contact, hydrothermal, burial, and ocean-floor metamorphism, as well as mixed lithification [7].
3.   Sample description
The dataset includes six data files: “Photomicrographs of sedimentary rocks for Nanjing University teaching.zip,” “Photomicrographs of igneous rocks for Nanjing University teaching.zip,” “Photomicrographs of metamorphic rocks for Nanjing University teaching.zip,” “Information table of sedimentary rocks for Nanjing University teaching.xls,” “Information table of igneous rocks for Nanjing University teaching.xls,” and “Information table of metamorphic rocks for Nanjing University teaching.xls.”
The dataset of instructional thin-section photographs of the three main types of rock consists of polarized micrographs of 324 thin sections of 108 rocks, each thin section containing eight or nine polarized-light micrographs from the same field. Each micrograph is the same as the color that can be seen with the naked eye, with the composition described in the information table. The micrographs in this dataset have been standardized to 1,280 × 1,024 or 4,908 × 3,264 pixels and saved in JPG format.
3.1   Dataset of sedimentary rocks for teaching at Nanjing University
The “Information table of sedimentary rocks for Nanjing University teaching.xls” data file consists of one clastic rock identification sheet and one other sedimentary rock identification sheet. The identification table contains basic and lithological feature information and the classification nomenclature of 84 teaching thin sections of 28 sedimentary rocks. The “Photomicrographs of sedimentary rocks for Nanjing University teaching.zip” data file consists of 699 pictures in JPG format.
The sedimentary rock thin sections for teaching at Nanjing University include pyroclastic rock, sandstone, shale and siltstone, limestone, dolomite, siliceous rock, and evaporite (Table 4). Of these, clastic rocks, pyroclastic rocks, limestone, shale, and sedimentary minerals are the most abundant. These thin sections aim to meet the needs of teaching, scientific research, and production practice related to sedimentary rocks.
Table 4   Statistics on teaching thin sections of sedimentary rocks from Nanjing University
Types of rockTotalNaming
pyroclastic rocks5Dacite crystalline fragment glass tuff, dacite fusion tuff, rhyolite fusion breccia tuff, dacite crystalline fragment glass fusion tuff, sinking tuff
Sandstone6Quartzose sandstone, glauconite quartzose sandstone, Feldspatho-quartzose sandstone、Feldspathic sandstone, Lithic sandstone, Quartzo-lithic wacke
Mudstone and siltstones6Calcareous siltstone, tuffaceous siltstone, shale, bentonite, kaolinite mudstone, siderite mudstone
Limestone5Biological chip microcrystalline limestone, crystal crinoid limestone, crystal agglomerated spherical limestone, crystal oolitic limestone, and crystal sandy limestone
Dolomite1Fine crystalline dolomite
Siliceous rock1Siliceous rock
Evaporite1Anhydrite
Other endogenous sedimentary rocks3Phosphorite, hematite rock, bauxite
3.2   Dataset of igneous rocks for teaching at Nanjing University
The “Information table of igneous rocks for Nanjing University teaching.xls” data file contains the basic and lithological feature information for 120 thin sections of 40 types of igneous rock. The “Photomicrographs of igneous rocks for Nanjing University teaching.zip” data file consists of 963 pictures in JPG format. These thin sections cover five types of igneous plutonic, shallow diagenetic, and extruded rock. More than 90% of the common igneous rock types (Figure 2, Table 5) can be found in this batch of thin sections. In addition, the common rock-forming mineral types, textures, and structures of igneous rocks (Figure 3) can be observed.
Table 5   Statistics on teaching thin sections of igneous rocks from Nanjing University
Types of rockTotalNaming
Ultrabasic (ultramafic) rock7Pure peridotite, pyroxene peridotite, iherzolite, glassy peridotite, plagioclase, titanite, kimberlite
Basic rock7Noritegabbro, diabase (2 species), peridotite, olivine basalt, porphyrite, sapphire
Neutral rock7Quartz diorite, quartz monzonite, syenite, pyroxene monzonite porphyry, hornblende andesite, trachy andesite, trachyte
Acid rock11Granodiorite, perlite granite, granite, biotite granite, muscovite granite, pegmatite, granite porphyry, rhyolite, spherulitic rhyolite, perlite, dacite
Alkaline rocks and related rocks8Sodalite aegirine—augite syenite, zoisite phonite, nephelinite, pseudoleucite phonite, spessartite, lantrolite, calcite carbonatite
3.3   Dataset of metamorphic rocks for teaching at Nanjing University
The “Information table of metamorphic rocks for Nanjing University teaching.xls” data set includes 40 kinds of metamorphic rock (Table 6) and the basic information and lithological characteristics of 120 teaching thin sections. The “Photomicrographs of metamorphic rocks for Nanjing University teaching.zip” data file consists of 972 JPG pictures. This batch of thin sections can be classified into 17 basic types of metamorphic rock (Figure 4). Most common metamorphic textures and structures (Figure 5) appear in these thin sections. In addition, in this batch of thin sections, more than 20 characteristic metamorphic minerals can be observed, such as cordierite, andalusite, wollastonite, serpentine, and pyroxene.
Table 6   Statistics on teaching thin sections of metamorphic rocks from Nanjing University
Types of rockTotalNaming
Mylonite2Mylonite (2 species)
Hornfel3Hornfel, cordierite hornfel, andalusite hornfel
Skarn3Cristobalite skarn, wollastonite skarn, garnet skarn
Marble3Diopside marble, tremolite marble (2 species)
Serpentine1Serpentine
greisen1greisen
Slate1Slate
Phyllite2Tourmaline phyllite, chlorite sericite phyllite
Schist9Chloritoid kyanite quartz schist, muscovite schist, blue amphibole schist, staurolite schist, sillimanite bimica schist, garnet bimica schist, garnet quartz schist, blue amphibole biotite schist, green schist, hornblende schist
Gneiss6Sillimanite gneiss, biotite plagioclastic gneiss, mixed petrified biotite plagioclase gneiss, garnet biotite potassium feldspar gneiss, sillimanite potassium feldspathic gneiss, kyanite potassium gneiss
Metagranulite1Metagranulite
Amphibolite1Amphibolite
Granulite2Granulite (2 species)
Eclogite1Eclogite
Migmatite1Gneissic migmatite
cataclasite1cataclasite
Others2Metamorphic diabase, metamorphic rhyolite
4.   Quality control and assessment
These thin section samples are of high quality and meet the standard thickness. During the shooting of the micrographs and the thin-section identification process, the quartz-particle interference colors observed in the same batch of thin sections were all first-class interference colors, indicating that the thickness of the thin sections meets the national standard of 0.03 mm.
In the process of microscope shooting, automatic exposure and automatic white balance were used so that the color was as consistent as possible with that observed by the naked eye and by the Nikon microscope camera system. The resolution of the pictures in JPG format is 1,280 × 1,024 or 4,908 × 3,264 pixels, ensuring the quality and clarity of the microphotograph.
5.   Value and significance
The various geological phenomena and descriptions contained in the microscopic images of this dataset can be used as physical reference standards. These photos can effectively supplement the professional concepts and descriptions that are divergent and difficult to explain.
This micrograph dataset consists of high-quality professional materials, which can be used for professional teaching, popular science, students' online self-study, and as an online museum.
These high-definition microscopic images can also be used as samples for computer machine learning and for collaborative research on the identification of rock thin sections through artificial intelligence. In addition, these unique and attractive microscopic images can also be used as materials for artistic appreciation or advertising, or design patterns for everyday goods.
6.   Usage notes
The data format of this dataset is simple, and the following points should be carefully noted when using it:
(1) All thin sections in the dataset are stored in the Department of Rock and Mineral Resources, School of Earth Sciences and Engineering, Nanjing University. If the micrographs provided in the above dataset do not meet the needs of the research, the author of this article or the Department of Rock and Mining, Nanjing University, can be contacted to apply for further use of these thin sections.
(2) The samples contained in this dataset are representative samples and can be used as a reference for general education, professional teaching, online teaching, etc.
(3) Some of the photos have deviations in terms of brightness and color, which are related to the instrument’s system deviation. Manual identification will not be affected, but computer reading may lead to inaccuracies in judgement. It is recommended that standardized preprocessing be used.
(4) The mineral content involved is an estimated value based on the area ratio of the microscopic image. An inaccurate value may reflect the relative content of each mineral.
(5) Images can be downloaded and used directly from the database. The geographic location and diagenetic background for each rock provided in the data information table can be used for a more comprehensive analysis.
Acknowledgments
Many thanks to all teachers from the Rock and Mineral Department of the School of Earth sciences and Engineering, Nanjing University for the collection and production of teaching thin sections. We are appreciate to the support for the informationization and online sharing of teaching thin sections from the Rock and Mineral Department.
[1] SHI Y. Professor Zhu Kezhen during the period of Nangao and Dongda. Geographical Research, 1987, 6(2): 57-63.
[2] WANG D. A brief history of the School of Earth Sciences and Engineering, Nanjing University. Nanjing: Nanjing University Press, 2011.
[3] HU X, LAI W. Chapter 6 Terrigenous clastic rocks. Lin Chunming. Sedimentary Petrology. Beijing: Science Press, 2019: 118-158.
[4] Department of Geology, Nanjing University. Different eras of South China granitoids and their relationship with mineralization. Beijing: Science Press, 1981.
[5] HU X, LAI W, ZHANG S, et al. Collection and information collection standard of sedimentary rock microscopic image dataset. China Scientific Data, 2020. (2020-03-02). DOI: 10.11922/ csdata.2020.0008.zh.
[6] XU X, QIU J. Igneous Rock Petrology. Beijing: Science Press, 2010.[7] HE T, LU L, LI S, et al. Petrology of metamorphic rocks. Beijing: Geological Publishing House, 1980.
Data citation
LAI W, JIANG XJX, QIU JS, et al. A photomicrograph dataset of rocks for petrology teaching at Nanjing University. Science Data Bank, 2020. (2020-07-24) DOI: 10.11922/sciencedb.j00001.00097.
Article and author information
How to cite this article
LAI W, JIANG JX, QIU JS, et al. A photomicrograph dataset of rocks for petrology teaching at Nanjing University. China Scientific Data, 2020, 5(3). (2020-08-28). DOI: 10.11922/csdata.2020.0071.zh.
Lai Wen
Mainly responsible for thin section photography and identification, paper writing.
born in Ganzhou, Jiangxi Province, Ph.D., assistant researcher, research direction is tectonic sedimentology.
Jiang Jingxin
Responsible for thin section identification and supplementary photography, data collation, paper revision.
born in Lanzhou, Gansu Province, PhD student, research field of paleoenvironmental sedimentology.
Qiu Jiansheng
Main tasks: review of igneous rock teaching thin section information table, revision of igneous rock part in the paper.
born in Ji'an City, Jiangxi Province, PhD, professor, research direction is magmatism and crust-mantle evolution, magmatism and mineralization.
Yu Jinhai
Responsible for review and revision of the metamorphic rock teaching thin sections information table, revision of the metamorphic rock part in the paper.
from Nanjing, Jiangsu Province, Ph.D., professor, research interests include metamorphism and crustal evolution, deep xenoliths in volcanic rocks, granite petrology, etc.
Hu Xiumian
Mainly responsible for review and revision of sedimentary rock teaching thin setion information table, design of datasets, revision of papers.
huxm@nju.edu.cn
born in Nanchang, Jiangxi Province, Ph.D., professor, research field of sedimentology.
Publication records
Published: Sept. 1, 2020 ( VersionsEN1
Released: July 28, 2020 ( VersionsZH2
Published: Sept. 1, 2020 ( VersionsZH4
References
中国科学数据
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