Selwynite

Formula: NaK(Be,Al)Zr2(PO4)4.2H2O

Origin of name: for Alfred Selwyn, Australian geologist

 

Crystal system: tetragonal

Crystal class: 4/m 2/m 2/m

Twinning:

Unit cell: 

 

Colour: purplish blue

Diaphaneity: transparent

Luster: vitreous

Habit: cavity fillings of intergrowths of indistinct radiating crystals and granular aggregates

Hardness: 4

Specific gravity: 2.94

Cleavage: 

Tenacity: 

Streak: pale lavender

 

Synonyms/varieties:

 

Comments: K analogue of gainesite

 

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