Perrierite-(Ce) crystals from ejecta of the Laacher See volcano, Eifel, in Germany were studied by X-ray single-crystal diffraction and electron microprobe analysis. The composition and crystal structure of this sample is discussed in relation to the known properties of the chevkinite group minerals and related synthetic compounds. Taking into account the modular character of the chevkinite minerals, based on a rutile and a silicate module, the preferred formation of either the perrierite or the chevkinite structure type is correlated with the formal charge of the rutile and silicate modules. The rutile module is expected to carry a negative charge, compensated by a positive charge of the silicate module. On average, the charge modulus is observed to be larger for the chevkinite-type module stacking. It can drop to zero in perrierite-type structures rich in Sr or Ca. In such cases, it is generally not expected to rise above two. The perrierite-(Ce) described in this study crystallizes in space group C2/m. The anisotropic oxygen and rare-earth element displacements observed in this crystal indicate a local domain structure of \(P2_1/a\) symmetry, when compared to the \(P2_1/a\) symmetry of the synthetic perrierite \(\hbox {La}_4\hbox {Mg}_2\hbox {Ti}_3\hbox {O}_8(\hbox {Si}_2\hbox {O}_7)_2\).

通过X射线单晶衍射和电子微探针分析研究了德国Eifel Laacher See火山喷口的钙钛矿（Ce）晶体。讨论了该样品的组成和晶体结构，涉及雪佛兰族矿物和相关合成化合物的已知特性。考虑到基于金红石和硅酸盐模块的白云母矿物的模块特性，钙铁矿或白云母结构类型的优选形成与金红石和硅酸盐模块的形式电荷相关。金红石模块预期带有负电荷，并由硅酸盐模块带正电荷补偿。平均而言，对于Chevkinite型组件堆叠，观察到的电荷模量更大。在富含Sr或Ca的钙锌矿型结构中，它可以降至零。在这种情况下，通常不希望其升至两个以上。本研究中描述的钙镁矿（Ce）在空间群中结晶C 2 /米。在该晶体中观察到的各向异性氧和稀土类元素的位移表示的局部结构域结构\（P2_1 / A \）对称，相对于当\（P2_1 / A \）合成perrierite的对称性\（\ hbox中{拉} _4 \ hbox {Mg} _2 \ hbox {Ti} _3 \ hbox {O} _8（\ hbox {Si} _2 \ hbox {O} _7）_2 \）。