Richterite

{{Short description|Sodium amphibole mineral}}

{{Infobox mineral

| name = Richterite

| category = Inosilicates

| image = Richterite-mrz156a.jpg

| caption = Richterite. Wilberforce, Monmouth Township, Haliburton County, Ontario, Canada.

| formula = Na(NaCa)Mg₅Si₈O₂₂(OH)₂#

| IMAsymbol = Rct{{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}}

| strunz = 9.DE.20

| system = Monoclinic

| class = Prismatic (2/m)
(same H-M symbol)

| symmetry = C2/m

| color = Brown, yellow, red, or green

| habit = Prismatic; acicular or asbestiform

| twinning = Simple or multiple parallel to {100}

| mohs = 5–6

| cleavage = Perfect

| fracture = Uneven, brittle

| luster = Vitreous

| streak = Pale yellow

| gravity = 3.0–3.5

| diaphaneity = Transparent to translucent

| opticalprop = Biaxial (−)

| refractive = nα = 1.615 nβ = 1.629 nγ = 1.636

| birefringence = δ = 0.021

| pleochroism = Strong: pale yellow, orange, and red

| 2V = 68° measured

| references = {{Cite web |url=http://www.handbookofmineralogy.com/pdfs/richterite.pdf |title=Handbook of Mineralogy |access-date=2014-05-11 |archive-date=2015-09-24 |archive-url=https://web.archive.org/web/20150924142253/http://www.handbookofmineralogy.com/pdfs/richterite.pdf |url-status=dead }}[http://www.mindat.org/min-3416.html Richterite on Mindat.org][http://www.webmineral.com/data/Richterite.shtml#.U2-IFYHMS1U Richterite data on Webmin]{{Cite web |url=http://pubsites.uws.edu.au/ima-cnmnc/ |title=IMA Master List |access-date=2014-05-12 |archive-date=2015-01-05 |archive-url=https://web.archive.org/web/20150105154315/http://pubsites.uws.edu.au/ima-cnmnc/ |url-status=dead }}

}}

Richterite is a sodium calcium magnesium silicate mineral belonging to the amphibole group. If iron replaces the magnesium within the structure of the mineral, it is called ferrorichterite; if fluorine replaces the hydroxyl, it is called fluororichterite. Richterite crystals are long and prismatic, or prismatic to fibrous aggregate, or rock-bound crystals. Colors of richterite range from brown, grayish-brown, yellow, brownish- to rose-red, or pale to dark green. Richterite occurs in thermally metamorphosed limestones in contact metamorphic zones. It also occurs as a hydrothermal product in mafic igneous rocks, and in manganese-rich ore deposits. Localities include Mont-Saint-Hilaire, Quebec, and Wilberforce and Tory Hill, Ontario, Canada; Långban and Pajsberg, Sweden; West Kimberley, Western Australia; Sanka, Myanmar; and, in the US, at Iron Hill, Colorado; Leucite Hills, Wyoming; and Libby, Montana. The mineral was named in 1865 for the German mineralogist Hieronymous Theodor Richter (1824–1898).