Mineral Environments
- Miarolitic Cavities -

     "Small, generally spherical miarolitic cavities rarely exceeding 10 cm in diameter, in nepheline syenite, are the mode of occurrence for a unique mineral assemblage rich in rare earth silicates and carbonates. The nepheline syenite is a dense, medium to dark gray rock, relatively uniform in color, texture and mineralogy."

Miarolitic cavity from MSH
© Quintin Wight

     "The miarolitic cavities are not uniformly distributed throughout the nepheline syenite, but tend to be concentrated in some areas while other areas are completely devoid of them. The reason for this localization is not well understood. The cavities are characteristically lined with a thin layer of foliated biotite and analcime on which the other minerals occur".*

* From Mineralogical Record Vol 21, Horváth L. and Gault R.A.