Garronite
Na₂Ca₅Al₁₂Si₂₀O₆₄ · 27H₂O

     Garronite is extremely rare at MSH. It has orthorhombic symmetry though it has a pseudo-tetragonal aspect.

PHYSICAL CHARACTERISTICS:

Color is usually pale yellow, orange-yellow or yellowish brown.
Luster is dull to greasy.
Diaphaneity is transparent to translucent.
Crystal System is orthorhombic; I4m2.
Crystal Habits include very small prisms that form globular and
   crude aggregates of tetragonal dipyramids to 2mm across.
Cleavage {100} and {010} are good.
Fracture is uneven.
Hardness is 4 - 4.5
Specific Gravity is approximately 2.15 g/cm³.
Streak is white.
Associated Minerals include aegirine, eudialyte, microcline,
   natrolite, sodalite and villiaumite.
Distinguishing Features: Crystal habit.
Origin: Named in 1962 after its discovery locality, in the
   Garron Plateau, County Antrim, Northern Ireland.

CLASSIFICATION:

REFERENCES:
MinRec 21:311 (1990), Dana 8:1662-1663 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

Legend

Garronite crystals
© Modris Baum