Magnetite and hematite iron oxides are minerals of great economic and scientific importance. The oxidation of magnetite to hematite is characterized as a topotaxial reaction in which the crystallographic orientations of the hematite crystals are determined by the orientation of the magnetite crystals. Thus, the transformation between these minerals is described by specific orientation relationships, called topotaxial relationships. This study presents electron‐backscatter diffraction analyses conducted on natural octahedral crystals of magnetite partially transformed into hematite. Inverse pole figure maps and pole figures were used to establish the topotaxial relationships between these phases. Transformation matrices were also applied to Euler angles to assess the diffraction patterns obtained and confirm the identified relationships. A new orientation condition resulting from the magnetite–hematite transformation was characterized, defined by the parallelism between the octahedral planes {111} of magnetite and rhombohedral planes of hematite. Moreover, there was a coincidence between one of the octahedral planes of magnetite and the basal {0001} plane of hematite, and between dodecahedral planes {110} of magnetite and prismatic planes of hematite. All these three orientation conditions are necessary and define a growth model for hematite crystals from a magnetite crystal. A new topotaxial relationship is also proposed: (111)_Mag || (0001)_Hem and  || .

中文翻译：

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定义磁铁矿-赤铁矿相变中赤铁矿的趋向晶体生长

磁铁矿和赤铁矿的氧化物是具有重大经济和科学意义的矿物。磁铁矿氧化成赤铁矿的特征是多轴反应，其中赤铁矿晶体的晶体学取向由磁铁矿晶体的取向决定。因此，这些矿物之间的转变通过特定的取向关系来描述，这种取向关系称为光轴关系。这项研究提供了对部分转变成赤铁矿的天然磁铁矿八面体晶体进行的电子背散射衍射分析。逆极图和极图用于建立这些相位之间的光轴关系。转换矩阵也应用于欧拉角，以评估获得的衍射图并确认已确定的关系。赤铁矿。而且，磁铁矿的八面体平面之一与赤铁矿的基面{0001}平面之间以及磁铁矿的十二面体平面{110}与赤铁矿的棱柱面之间存在重合。所有这三个取向条件都是必需的，并定义了磁铁矿晶体中赤铁矿晶体的生长模型。还提出了新的光轴关系：（111）_Mag  || （0001）_下摆和 || 。