Ludwigite

{{Infobox mineral

| name = Ludwigite

| category = Borate mineral

| boxwidth =

| boxbgcolor =

| image = Ludwigite-242641.jpg

| imagesize = 260px

| caption = Radial aggregates of lustrous, black, metallic, acicular ludwigite crystals to 0.5 cm, from Alta Stock, Salt Lake County, Utah, USA.

| formula = Mg₂Fe³⁺BO₅

| IMAsymbol = Ldw{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| molweight = 195.26 g/mol

| strunz = 6.AB.30

| system = Orthorhombic

| class = Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)

| symmetry = Pbam

| unit cell = a = 9.26, b = 12.26
c = 3.05 [Å]; Z = 4

| color = Pitch-black, olive-black

| habit = Massive – fibrous commonly in fanlike to felted aggregates

| cleavage = [001] Perfect

| fracture = Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments.

| mohs = 5.5

| luster = Silky to submetallic

| refractive = n_α = 1.830 – 1.850 n_β = 1.830 – 1.850 n_γ = 1.940 – 2.020

| opticalprop = Biaxial (+)

| birefringence = δ = 0.110 – 0.170

| pleochroism = X = Y = dark green; Z = dark reddish brown

| 2V = Measured: 20° to 45°

| streak = Greenish black

| gravity = 3.6 – 3.8

| melt =

| fusibility =

| diagnostic =

| solubility = Slowly soluble in acid

| diaphaneity = Opaque, translucent in thin fragments

| alteration = limonite

| references = [http://rruff.geo.arizona.edu/doclib/hom/ludwigite.pdf Handbook of Mineralogy]

}}

Ludwigite is a magnesium-iron borate mineral: Mg₂FeBO₅.

Ludwigite typically occurs in magnesian iron skarn and other high temperature contact metamorphic deposits. It occurs in association with magnetite, forsterite, clinohumite and the borates vonsenite and szaibelyite. It forms a solid solution series with the iron(II)-iron(III) borate mineral vonsenite.

It was first described in 1874 for an occurrence in Ocna de Fier, Banat Mountains, Caraș-Severin County, Romania and named for Ernst Ludwig (1842–1915), an Austrian chemist at the University of Vienna.[http://www.mindat.org/min-2454.html Ludwigite on Mindat.org]

File:Forsterite-Ludwigite-34581.jpg crystal from Sapat Gali, Kohistan District, Pakistan. Size 2.8 x 2 x 1.1 cm.]]

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