RINKITE-(Ce)

Rinkite-(Ce) – (Ca3Ce)Na(NaCa)Ti(Si2O7)2(OF)F2 – is a very rare sorosilicate that occurs in uncommon types of plutonic rocks. It has no significance as an ore.

It was reclassified by the IMA (International Mineralogical Association) in 2016, with its name changing from “rinkite” to “rinkite-(Ce).”

It may contain various impurities, such as Mn, Mg, K, H₂O, Fe, Zr, and rare earth elements (Th, Y, La).

1. Characteristics

Crystal system: Monoclinic sphenoidal        

Color: Yellow, yellowish-green, brown. Alters to a dull greenish or yellowish-brown.  

Habit: Prismatic, tabular, massive. Crystals up to 10 cm.

Cleavage: {100} good. Deep striations.

Tenacity: Brittle.     

Twinning: Polysynthetic on {100}. Lamellar.

Fracture: Conchoidal, irregular.

Mohs Hardness: 4 – 5

Parting: No.  

Streak: Pale yellow, brownish-gray, white.

Lustre: Vitreous on fractures, resinous on cleavage planes.

Diaphaneity: Transparent.     

Density (g/cm³): 3.5

 

2. Geology and Deposits

It occurs in nepheline syenites, sodalite syenites, and related pegmatites.

 

3. Mineral Associations

It occurs with common minerals, such as feldspars (microcline), feldspathoids (sodalite, nepheline), amphiboles (arfvedsonite), pyroxenes (aegirine), fluorite, and fluorapatite.

Its specific paragenesis includes rare minerals such as those of the eudialyte group, lavenite, steenstrupine, leucophanite, wöhlerite, fersmanite, astrophyllite, rosenbuschite, and villiaumite.

 

4. Transmitted Light Microscopy

Refraction indices: nα: 1.665    nβ: 1.668     nγ: 1.681

PLANE POLARIZED LIGHT – PPL

Color / Pleochroism: Vivid red, with subtle pleochroism in shades of yellow.  

Relief: Moderate.     

Cleavage: {100} good.

Habits: Prismatic, tabular, massive.

CROSSED POLARIZED LIGHT – XPL

Birefringence and Interference Colors: Maximum birefringence of 0.016, corresponding to 1st-order colors up to orange: gray, white, yellow, and orange.   

Extinction: No information available.   

Elongation sign: No information available.   

Twins: Polysynthetic along {100}, also lamellar.  

Zoning: No information available.    

CONVERGENT LIGHT

Character: B(+)    

2V angle: 43º – 87º

Alterations: No information available.    

May be confused with: No information available. 

Caption.

5. Reflected Light Microscopy

Reflected-light microscopy is clearly not the recommended analytical method for the identification of rinkite-(Ce). However, preparing a thin section or polished section is important for identifying the opaque minerals that occur in association with rinkite-(Ce).

Sample preparation: xx

PLANE POLARIZED LIGHT – PPL

Reflection color: xx

Pleochroism: xx

Reflectivity: xx

Bireflectance:  xx

CROSSED POLARIZED LIGHT – XPL

Isotropy / Anisotropy: xx

Internal reflections:  xx

May be confused with: xx

General Characteristics: xx

Caption.