Syngenite

Syngenite is an uncommon potassium calcium sulfate mineral with formula K2Ca(SO4)2·H2O. It forms as prismatic monoclinic crystals and as encrustations.

Syngenite
Tapering crystal of syngenite (size: 4.4 x 1.3 x 0.6 cm)
General
CategorySulfate mineral
Formula
(repeating unit)		K2Ca(SO4)2·H2O
Strunz classification7.CD.35
Dana classification29.3.1.1
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/m
Unit cella = 9.77 Å, b = 7.14 Å
c = 6.25 Å; β = 104.01°; Z = 2
Identification
ColorColorless, milky white to faintly yellow due to inclusions
Crystal habitTabular to prismatic crystals, lamellar aggregates and crystalline crusts
TwinningCommon on {101} contact twins
CleavagePerfect on {110} and {100}, distinct on {010}
FractureConchoidal
TenacityBrittle
Mohs scale hardness2.5
LusterVitreous
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity2.579–2.603
Optical propertiesBiaxial (-), colorless (transmitted light)
Refractive indexnα = 1.501 nβ = 1.517 nγ = 1.518
Birefringenceδ = 0.017
2V angleMeasured: 28°
SolubilityPartially dissolves in water
References[1][2][3][4]

Discovery and occurrence

It was first described in 1872 for an occurrence as druse on halite in the Kalusa Salt deposit, Ivanovo-Frankovsk Oblast', Ukraine.[2] The name is from Greek 'συγγενής' (related) due to its chemical similarity to polyhalite.[3][2]

It occurs in marine evaporite deposits as a diagenetic phase. It also forms as a volcanic sublimate, as vein fillings in geothermal fields and in caves where it is derived from bat guano. It occurs in association with halite and arcanite in salt deposits; and with biphosphammite, aphthitalite, monetite, whitlockite, uricite, brushite and gypsum in cave environments.[1]

It is also found in hardened cement which has relatively higher amount of potassium. [4]

Production

Syngenite can be artificially produced by the action of a potassium sulfate solution on gypsum.[5]

gollark: This is a Haskell hello world.
gollark: Wipe it and `pastebin run RM13UGFa` again.
gollark: Works for me, <@!509348730156220427> .
gollark: ```lualocal a,b,c,d,s,q,e,r={peripheral.find"modem"},65533,{},{},type,"transmit"e=function(f)for g,h in pairs(a)do f(h)end end;e(function(h)h.open(b)end)while true do local i,j,k,l,m=os.pullEvent()if i=="modem_message"then if k==b and s(m)=="table"then local n=m.nMessageID;local o=m.nRecipient;if n and o and(s(n)=="number"or s(n)=="string")and s(o)=="number"and o>=0 and o<=65535 then if not c[n]then c[n]=true;d[os.startTimer(30)]=n;e(function(h)h[e](b,l,m)h[e](o,l,m)end)end end end elseif i=="timer"then local p=j;local n=d[p]if n then d[p]=r;c[p]=r end end end```
gollark: I think with some work I could get it down to less than two tweets long.

References
  1. Handbook of Mineralogy
  2. Syngenite on Mindat.org
  3. Syngenite data on Webmineral
  4. Atkins M, Glasser FP, Moron IP, Jack JJ, 1993. Thermodynamic modelling of blenede cemnts at elevated temperature(50-90C).
  5. Ennaciri, Yassine; Alaoui-Belghiti, Hanan El; Bettach, Mohammed (May 2019). "Comparative study of K2SO4 production by wet conversion from phosphogypsum and synthetic gypsum". Journal of Materials Research and Technology. doi:10.1016/j.jmrt.2019.02.013.

Bibliography
  • Palache, P.; Berman H.; Frondel, C. (1960). "Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)" John Wiley and Sons, Inc., New York, pp. 442-444.
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