The margarosanite group (now officially confirmed by IMA-CNMNC) consists of triclinic Ca-(Ba, Pb) cyclosilicates with three-membered [Si3O9]6– rings (3R), with the general formula AB2Si3O9, where A = Pb, Ba and Ca and B = Ca. A closest-packed arrangement of O atoms parallel to (101) hosts Si and B cations in interstitial sites in alternating layers. The 3R layer has three independent Si sites in each ring. Divalent cations occupy three independent sites: Ca in B occupies two nonequivalent sites, Ca1 (8-fold coordinated), and Ca2 (6-fold coordinated). A (=Ca3) is occupied by Pb2+ (or Ba2+) in 6+4 coordination, or 6+1 when occupied by Ca; this third site occurs within the 3R-layer in a peripheral position. Three minerals belong to this group: margarosanite (ideally PbCa2Si3O9), walstromite (BaCa2Si3O9) and breyite (CaCa2Si3O9). So far, no solid solutions involving the Ca1 and Ca2 sites have been described. Therefore, root names depend on the composition of the Ca3 site only. Isomorphic replacement at the Ca3 sites has been noted. We here report data on a skarn sample from the Jakobsberg Mn–Fe oxide deposit, in Värmland, Sweden, representing intermediate compositions on the walstromite–margarosanite binary, in the range ca. 50–70% mol.% BaCa2Si3O9. The Pb-rich walstromite is associated closely with celsian, phlogopite, andradite, vesuvianite, diopside and nasonite. A crystal-structure refinement (R1 = 4.8%) confirmed the structure type, and showed that the Ca3 (Ba, Pb) site is split into two positions separated by 0.39 Å, with the Ba atoms found slightly more peripheral to the 3R-layers.

margarosanite组（现已由IMA-CNMNC正式确认）由具有三元[Si 3 O 9 ] 6–环（3R）的三斜晶Ca-（Ba，Pb）环硅酸盐组成，通式为AB 2 Si 3 O 9，其中A = Pb，Ba和Ca，B =Ca。与（101）平行的O原子最紧密堆积的排列在交替层的间隙位置中包含Si和B阳离子。3R层在每个环中具有三个独立的Si位点。二价阳离子占据三个独立位点：B中的Ca占据两个非等价位点，Ca 1（8倍配位）和Ca2（6倍协调）。A（= Ca 3）被Pb 2+（或Ba 2+）占据6 + 4配位，或6 + 1被Ca占据；第三个位点出现在3R层的外围位置。三种矿物属于这一类：玛格岗石（理想的是PbCa 2 Si 3 O 9），方铁矿（BaCa 2 Si 3 O 9）和褐铁矿（CaCa 2 Si 3 O 9）。迄今为止，还没有描述涉及Ca 1和Ca 2位点的固溶体。因此，根名取决于Ca的组成仅3个网站。已经注意到在Ca 3位点的同构置换。我们在此报告的数据来自瑞典Värmland的Jakobsberg Mn-Fe氧化物矿床的矽卡岩样品，其代表了辉石-玛格罗南岩二元系中的中间成分，范围在ca左右。50–70％mol。％BaCa 2 Si 3 O 9。富含Pb的辉石与硅藻土，金云母和红土，维苏石，透辉石和钠钠榴石密切相关。晶体结构的细化（R 1 = 4.8％）证实了结构类型，并表明Ca 3（Ba，Pb）位点被分成两个相距0.39Å的位置，而Ba原子在3R的外围更细一些层。