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(Na,Ce)(Y,REE)(HCO3)(OH)3 · 4H2O
Honey-yellow to white
2 - 3
Named in honor of Thomas Henry Clark (1893-1996), Professor of Geology, McGill University, Montreal, Quebec (Canada), noted for his studies of the geology of the St. Lawrence Lowlands.
This page provides mineralogical data about Thomasclarkite-(Y).

Classification of Thomasclarkite-(Y)

Approved 1997

D : Carbonates with additional anions, with H2O
C : With large cations URL:
Please feel free to link to this page.

Type Occurrence of Thomasclarkite-(Y)

Physical Properties of Thomasclarkite-(Y)

Diaphaneity (Transparency):
Transparent, Translucent
Honey-yellow to white
Hardness (Mohs):
2 - 3

Crystallography of Thomasclarkite-(Y)

Crystal System:
Class (H-M):
2 - Sphenoidal
Space Group:
Space Group Setting:
Cell Parameters:
a = 4.556Å, b = 13.018Å, c = 4.556Å
β = 90.15°
a:b:c = 0.35 : 1 : 0.35
Unit Cell Volume:
V 270.2 ų

Optical Data of Thomasclarkite-(Y)

Uniaxial (-)
RI values:
nω = 1.540 nε = 1.400
Max Birefringence:
δ = 0.140
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:

Chemical Properties of Thomasclarkite-(Y)

(Na,Ce)(Y,REE)(HCO3)(OH)3 · 4H2O
All elements listed in formula:

Relationship of Thomasclarkite-(Y) to other Species

5.DC.05Ancylite-(Ce)SrCe(CO3)2(OH) · H2O
5.DC.05Calcioancylite-(Ce)(Ca,Sr)Ce(CO3)2(OH) · H2O
5.DC.05Gysinite-(Nd)Pb(Nd,La)(CO3)2(OH) · H2O
5.DC.05Ancylite-(La)Sr(La,Ce)(CO3)2(OH) · H2O
5.DC.10Kamphaugite-(Y)Ca(Y,REE)(CO3)2(OH) · H2O
5.DC.15SheldrickiteNaCa3(CO3)2F3 · H2O
5.DC.25Peterbaylissite(Hg2+)1.5(CO3)(OH) · 2H2O
5.DC.30Clearcreekite(Hg2+)1.5(CO3)(OH) · 2H2O
5.DC.35NiveolaniteNaBe(CO3)(OH) · 2H2O

Other Names for Thomasclarkite-(Y)

Name in Other Languages:

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Thomasclarkite-(Y)

Reference List:
GRICE, J.D., and GAULT, R.A. (1998) Thomasclarkite (Y), a new sodium rare earth element bicarbonate mineral species from Mont Saint Hilaire, Quebec. Canadian Mineralogist, 36, 1293 1300.

Internet Links for Thomasclarkite-(Y)

The following Thomasclarkite-(Y) specimens are currently listed for sale on

Localities for Thomasclarkite-(Y)

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Canada (TL)
  • Québec
    • Montérégie
      • La Vallée-du-Richelieu RCM
        • Mont Saint-Hilaire
Grice, J.D. & Gault, R.A. (1998), Thomasclarkite-(Y), a new sodium-rare-earth-element bicarbonate mineral species from Mont Saint-Hilaire, Quebec. Canadian Mineralogist: 36: 1295-1301.
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