Bulachite specimens from Cap Garonne, France, comprise two intimately mixed hydrated aluminium arsenate minerals with the same Al:As ratio of 2:1 and with different water contents. The crystal structures of both minerals have been solved using data from low-dose electron diffraction tomography combined with synchrotron powder X-ray diffraction. One of the minerals has the same powder X-ray diffraction pattern (PXRD) as for published bulachite. It has orthorhombic symmetry, space group Pnma with unit-cell parameters a = 15.3994(3), b = 17.6598(3), c = 7.8083(1) Å and Z = 4, with the formula [Al6(AsO4)3(OH)9(H2O)4]⋅2H2O. The second mineral is a higher hydrate with composition [Al6(AsO4)3(OH)9(H2O)4]⋅8H2O. It has the same Pnma space group and unit-cell parameters a = 19.855(4), b = 17.6933(11) and c = 7.7799(5) Å i.e. almost the same b and c parameters but a much larger a parameter. The structures are based on polyhedral layers, parallel to (100), of composition [Al6(AsO4)3(OH)9(H2O)4] and with H-bonded H2O between the layers. The layers contain [001] spiral chains of edge-shared octahedra, decorated with corner connected AsO4 tetrahedra that are the same as in the mineral liskeardite. The spiral chains are joined together by octahedral edge-sharing to form layers parallel to (100). Synchrotron PXRD patterns collected at different temperatures during heating of the specimen show that the higher-hydrate mineral starts transforming to bulachite when heated to 50°C, and the transformation is complete between 75 and 100°C.

法国Cap Garonne的针铁矿样品包含两种混合的水合砷酸铝矿物，它们的Al：As比例为2：1，含水量不同。使用来自低剂量电子衍射层析成像和同步加速器粉末X射线衍射的数据已解析了两种矿物的晶体结构。一种矿物具有与公开的球藻石相同的粉末X射线衍射图（PXRD）。它具有正交对称性，具有单元格参数a = 15.3994（3），b = 17.6598（3），c = 7.8083（1）Å和Z = 4的空间群Pnma，其公式为[Al 6（AsO 4）3（OH）9（H 2 O）4 ]⋅2H 2 O.第二矿物是与组合物[铝更高的水合物6（ASO 4）3（OH）9（H 2 O）4 ]⋅8H 2 O.它具有相同的晶Pnma空间群和晶胞参数一个= 19.855（4），b = 17.6933（11）和C ^ = 7.7799（5）即，几乎是相同的b和c ^参数，但更大的一个参数。该结构基于平行于（100）且成分为[Al 6（AsO4）3（OH）9（H 2 O）4 ]，并与H-键合的H 2澳层之间。这些层包含边缘共享的八面体的[001]螺旋链，装饰有角连接的AsO 4四面体，与矿物LSK中的相同。螺旋链通过八面体边缘共享连接在一起，形成平行于（100）的层。在加热样品过程中在不同温度下收集的同步加速器PXRD图谱显示，当加热到50°C时，高水合物矿物质开始转变为球铁矿，并且在75至100°C之间完成了转变。