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本文报道了天然Ⅱ型ＣａＣＯ３ 矿物。该矿物发现于海洋表层沉积物，成分与方解石、文石及六方球方解石相同，但结构完全不同，它们共同组成了天然ＣａＣＯ３ 的同质多象变体。天然Ⅱ型ＣａＣＯ３ 矿物的空间群为Ｐ２１／ｃ，单位轴长为ａ０＝ ０．６２９０±０．０００２ ｎｍ ，ｂ０＝ ０．４９３４±０．０００２ ｎｍ ，ｃ０＝ ０．７９７９±０．０００３ｎｍ ，β＝ １０７．５７１°±０．００２°，Ｚ＝ ４，单胞体积为０．２３６０５±０．１７４９ｎｍ ３；理论密度为２．８２ ｇ／ｃｍ ３，实测值为２．７６ ｇ／ｃｍ ３；实测硬度Ｈ＝ ４。天然Ⅱ型ＣａＣＯ３ 矿物是在深水环境中较高静水压力下形成的珊瑚体生物矿物。
This paper reports the natural type Ⅱ CaCO3 minerals. The mineral is found in marine surficial sediments and has the same composition as calcite, aragonite and hexagonal calcite, but with completely different structures that together form a homogeneous multimodal variant of natural CaCO3. The space group of natural type II CaCO3 minerals is P21 / c, the unit axis length is a0 = 0.6290 ± 0.0002 nm, b0 = 0.4934 ± 0.0002 nm, c0 = 0.7979 ± 0.0003 nm, β = 107.571 ° ± 0.002 °, Z = 4, the unit cell volume is 0.23605 ± 0.1749 nm 3; the theoretical density is 2.82 g / cm 3 and the measured value is 2.76 g / cm 3; The measured hardness H = 4. Natural Type II CaCO3 minerals are coral bio minerals formed at higher hydrostatic pressures in deep water environments.