lavendulan

{{Infobox mineral | name = Lavendulan | category = Arsenate mineral | boxwidth = 24 | boxbgcolour = | image = Lavendulan-112544.jpg | imagesize = 260px | caption = | formula = | IMAsymbol = Lvd | molweight = 1,062.00 g/mol | strunz = 8.DG.05 | dana = 42.9.4.2 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = P21/n | color = Blue or greenish blue | habit = Thin botryoidal crusts of minute radiating fibers or thin rectangular, pseudo-orthorhombic plates | lattice = | twinning = Common | cleavage = Good on {010}, distinct on {100} and {001} | fracture = Uneven | tenacity = Brittle | mohs = to 3 | luster = Vitreous to waxy, satiny in aggregates | refractive = Nx = 1.645 Ny = 1.715 Nz = 1.725 Nx = 1.660 Ny = 1.715 Nz = 1.734 Nx = 1.66 Ny = 1.715 Nz = 1.734 omega = 1.748 epsilon = 1.645 | opticalprop = Biaxial (−), nearly uniaxial (−) | birefringence = | pleochroism = O = pale blue to pale greenish blue, E = blue to greenish blue | streak = Light blue | gravity = 3.54 3.84 | density = | melt = | fusibility = | diagnostic = | solubility = Easily soluble in hydrochloric acid | diaphaneity = Translucent | other = Not radioactive | references = }} Lavendulan is an uncommon arsenate mineral in the lavendulan group. It is known for its characteristic intense electric blue colour. Lavendulan is very similar to lemanskiite, the analogue trihydrate mineral, to the point of them being considered dimorphs. Lemanskiite is tetragonal, but lavendulan is monoclinic. 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.