greenockite

{{Infobox mineral

| name = Greenockite

| category = Sulfide mineral

| image = Greenockite-259580.jpg

| imagesize = 260px

| caption = Greenockite crystals from Tsumeb Mine, Namibia (Picture width 1 mm)

| formula = CdS

| IMAsymbol = Gnk{{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 = 144.48

| strunz = 2.CB.45

| system = Hexagonal

| class = Dihexagonal pyramidal (6mm)
(same H-M symbol)

| symmetry = P6₃mc

| unit cell = a = 4.136
c = 6.713 [Å]; Z = 2

| color = Honey yellow, citron yellow, orange yellow

| habit = Colloform – forming from a gel or colloidal mass; encrustations – forms crust-like aggregates on matrix; radial – crystals radiate from a center without producing stellar forms (e.g. stibnite)

| twinning = Rare on {11{{overline|2}}2} forming trillings

| cleavage = Distinct on {11{{overline|2}}2}, imperfect on {0001}

| fracture = Conchoidal

| tenacity = Brittle

| mohs = 3.0–3.5

| luster = Adamantine to resinous

| refractive = n_ω = 2.529 n_ε = 2.506

| opticalprop = Uniaxial (−)

| birefringence = δ = 0.023

| pleochroism = Weak

| streak = Yellow orange to brick red

| gravity = 4.8–4.9

| melt =

| fusibility =

| diagnostic =

| solubility =

| diaphaneity = Nearly opaque to translucent

| fluorescence = yellow-orange fluorescence under UV when rich in zinc{{citation needed|date=May 2014}}

| other = Toxic

| references = [http://rruff.geo.arizona.edu/doclib/hom/greenockite.pdf Handbook of Mineralogy][http://www.mindat.org/min-1746.html Mindat][http://webmineral.com/data/Greenockite.shtml Webmineral]

| SMILES = [CdH2-2]1[S+2]47[CdH-2]2[S+2][CdH-2]3[S+2]8([CdH2-2][SH+2]([CdH2-2]4)[CdH2-2]6)[CdH-2]4[S+2][CdH-2]5[S+2]6([CdH2-2]6)[Cd-2]78[S+2]78[CdH-2]([SH+2]69)[SH+2]5[CdH2-2][SH+2]4[CdH-2]7[SH+2]3[CdH2-2][SH+2]2[CdH-2]8[SH+2]1[CdH2-2]9

| Jmol = [CdH2-2]1[SH+2]([CdH2-2]6)[CdH2-2][SH+2]7[CdH-2]2[S+2][Cd-2]3([S+2][CdH-2]9[S+2]5)[S+2]18[Cd-2]45[S+2][CdH-2]5[SH+2]6[Cd-2]78[S+2]78[CdH2-2][SH+2]5[CdH2-2][S+2]4([CdH2-2][SH+2]9[CdH2-2]4)[CdH-2]7[S+2]34[CdH2-2][SH+2]2[CdH2-2]8

}}

Greenockite, also cadmium blende or cadmium ochre (obsolete) is a rare cadmium bearing metal sulfide mineral consisting of cadmium sulfide (CdS) in crystalline form. Greenockite crystallizes in the hexagonal system. It occurs as massive encrustations and as hemimorphic six-sided pyramidal crystals which vary in color from a honey yellow through shades of red to brown. The Mohs hardness is 3 to 3.5 and the specific gravity is 4.8 to 4.9.

Greenockite belongs to the wurtzite group and is isostructural with it at high temperatures. It is also isostructural with sphalerite at low temperatures. It occurs with other sulfide minerals such as sphalerite and galena, and is the only ore mineral of cadmium. Most cadmium is recovered as a byproduct of copper, zinc, and lead mining. It is also known from the lead-zinc districts of the central United States.

It was first recognized in 1840 in Bishopton, Scotland, during the cutting of a tunnel for the Glasgow, Paisley and Greenock Railway. The mineral was named after the land owner Lord Greenock (1783–1859).{{Cite web |url=http://www.hmag.gla.ac.uk/John/huntmin/greenock.htm |title=Glasgow museum site |access-date=2005-08-02 |archive-url=https://web.archive.org/web/20120716222609/http://www.hmag.gla.ac.uk/John/huntmin/greenock.htm |archive-date=2012-07-16 |url-status=dead }}