Abstract：The Qingtian stone is one the Four famous Seal Stones in China, which is from Qingtian County, Zhejiang Province. All of the Qingtian Stones are primary ore, belonging to mined Seal Stone. The digged Qingtian Stone has various colors. The red Qingtian stone is not an abundant species among Qingtian stones, which shows unique dark reddish brown. Four kinds of red Qingtian Stones have been studied in this paper, which are Jelly Flower-red Stone, Flower-red Stone, Pomegranate-red stone and Orange-red stone. Their mineral composition and color causingare studied by means of optical microscopy, X-ray powder diffraction (XRD), and Raman spectrum (LRM). Under optical microscopy, the red color distribution had been carefully observed in the slices of four kinds of red Qingtian Stones. The red parts of Jelly Flower-red Stone and Orange-red stone are composed of granulose or massive disseminated in the matrix. But red parts of Pomegranate-red Stone and Flower-red Stone are composed of dots or nervation disseminated in the matrix. In XRD tests, the main and minor mineral compositions had been studied, and the type of the stone had been decided. The main miner composition is pyrophyllite in Jelly Flower-red Stone, Flower-red Stone and Orange-red Stone. So they belong to Pyrophyllite-type Qingtian Stone. Pyrophyllite has two polymorphic types, which are 1Tc and 2M. According to the form and site of the diffraction peaks of XRD pattern at 19°~ 22° (2θ) and 28~31°(2θ), Jelly Flower-red Stone is mainly composed of 2M pyrophyllite, and a minor of 1Tc pyrophyllite. Flower-red Stone and Pomegranate-red Stone are mainly composed of 2M pyrophyllite. The minor compositions are dickite in Jelly Flower-red Stone, quartz in Flower-red Stone, muscovite in Pomegranate-red Stone, respectively. However, the main composition is dickite in Orange-red Stone, which belongs to Dickite-type Qingtian Stone. Dicket has order→disorder structure, which can be decided by XRD diffraction peaks at (020), (110), (112). The minor composition of Orange-red Stone is quartz. Minor and trace minerals in the red Qingtian Stones were tested by LRM. And LRM was mainly used to detect minerals at red parts, and to decide the color causation of red Qingtian Stones. The results indicate that all of the four red Qingtian Stones contain hematite. On the other hand, Jelly Flower-red Stone also contains hematite and pyrophyllite. Flower-red Stone also contains a lot of quartz and minor pyrophyllite and rutile. Pomegranate-red Stone also contains pyrophyllite and rutile. Orange-red Stone also contains quartz. Red color is caused by hematite in Jelly Flower-red Stone, Flower-red Stone and Orange-red Stone, but is caused by rutile in Pomegranate-red Stone. Therefore, all of the four studied Qingtian Stones are colored by impurity minerals.
Key words：Qingtian stone; Hematite; Rutile; Mineral composition; Color causing
卓成城，陈 涛. 4种红色青田石的矿物成分与谱学特征[J]. 光谱学与光谱分析, 2019, 39(10): 3232-3236.
ZHUO Cheng-cheng, CHEN Tao. Study on Mineral Composition and Spectroscopy Characteristics of Four Kinds of Red Qingtian Stones. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(10): 3232-3236.
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