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Lavendulan is an uncommon copper arsenate mineral, known for its characteristic intense electric blue colour. It belongs to the lavendulan group, which has four members: * Lavendulan NaCaCu5(AsO4)4Cl.5H2O * Lemanskiite NaCaCu5(AsO4)4Cl.5H2O * Sampleite NaCaCu5(PO4)4Cl.5H2O * Zdenĕkite NaPbCu5(AsO4)4Cl.5H2O Lemanskiite and lavendulan are dimorphs; they have the same formula, but different structures. Lemanskiite is tetragonal, but lavendulan is monoclinic.〔Canadian Mineralogist (2006) 44: 523-531〕 Lavendulan has the same structure as sampleite, and the two minerals form a series.〔 It is the calcium analogue of zdenĕkite, and the arsenate analogue of sampleite. Lavendulan was originally named for the lavender color of the "type" specimen, which has since been determined to be a mixture with no relationship to modern lavendulan. The mineral which is now called lavendulan is not a lavender blue color, and has no relationship to the “type” material from Annaberg.〔 It often contains potassium, cobalt and nickel as impurities. == Unit cell == Although lavendulan is monoclinic, the angle β is very close to 90°, making the mineral pseudo-orthorhombic. Most references describe the lavendulan unit cell as an orthorhombic cell containing 8 formula units (Z=8) but Mindat.org describes a monoclinic unit cell with the length of the c axis halved, and only 4 formula units per unit cell (Z=4) and space group P21/n.〔 Unit cell parameters are reported as *a=9.73 Å, b=41.0 Å, c=9.85 Å, Z=8 〔Gaines et al (1997) Dana’s New Mineralogy. Wiley〕 *a = 9.815 Å, b = 40.394 Å, c = 9.99 Å, Z = 8 〔http://www.webmineral.com/data/Lavendulan.shtml〕 *a = 9.73 Å, b = 41.0 Å, c = 9.85 Å, Z = 8 〔 *a = 10.011 Å, b = 19.478 Å, c = 10.056 Å, β = 90.37° Z=4〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「lavendulan」の詳細全文を読む スポンサード リンク
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