Sahamalite-(Ce)

sahamalite-(Ce)

bastnasite

parisite

ankerite

Images

Formula: Ce₂Mg(CO₃)₄
Anhydrous carbonate of cerium and magnesium
Crystal System: Monoclinic
Specific gravity: 4.30 measured, 4.30 calculated
Streak: White
Colour: Colourless
Solubility: More resistant to acids than most normal carbonates
Environments

Carbonatites
Hydrothermal environments

Localities

At the Kangankunde Carbonatite Complex, Balaka, Southern Region, Malawi, sahamalite-(Ce) is associated with synchysite, monazite, strontianite and quartz (HOM).

At the type locality, the Mountain Pass Mine, Mountain Pass, Mountain Pass District, Clark Mts, San Bernardino County, California, USA, carbonate-rich rocks, composed essentially of calcite, dolomite, baryte, quartz and bastnäsite, occur as veins and irregular bodies in foliated metamorphic rocks and in alkalic igneous rocks, including shonkinite, syenite and quartz syenite. The largest of the irregular carbonate-rich bodies, locally referred to as the Sulfide Queen, contains baryte and bastnäsite throughout, but sahamalite-(Ce) has been detected only in an area of about one acre in the southwestern part of the exposed Sulfide Queen body.
Sahamalite-(Ce) occurs in a medium- to coarse- grained, light to dark brown baryte-dolomite rock. Dolomite is thought to be the oldest mineral, and its formation was followed by the introduction of bastnäsite and baryte; sahamalite-(Ce) and parisite accompanied by quartz are believed to be the last minerals to crystallise. The order of rare earth mineral crystallisation - bastnäsite, parisite, sahamalite-(Ce) - is consistent with a decreasing availability of fluorine; bastnäsite and parisite contain essential fluorine, whereas sahamalite-(Ce) has none. It is inferred that parisite and sahamalite-(Ce) have formed from dolomite and bastnäsite under hydrothermal conditions (AM 38.741-754).
Other associated minerals include ankerite and hematite (HOM).
Sahamalite-(Ce) from the Mountain Pass Mine - Image

At the Durham Ranch paralava occurrence, Reno Junction, Campbell County, Wyoming, USA, sahamalite-(Ce) is associated with dorrite, esseneite, titanium-bearing andradite, magnetite – magnesioferrite – spinel, plagioclase, gehlenite–åkermanite, wollastonite, ulvospinel, nepheline and apatite. (HOM).

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