Kalsilite
A drill core sample from Mount Poachvumchorr, Khibiny, the rock is fine
grained rischorrite. What you see is white potassium
feldspar and gray foid minerals. Because rischorrites are relatively rich in
potassium compared to the rest of Khibiny, the foid mineral
is not only nepheline, but also contains small amounts of Kalsilite. Both
Nepheline and Kalsilite look identical.
This core is from a depth of 400 meters. At this depth there is a 15 meter
thick rischorrite body at Poachvumchorr.
[photo/collection: Maurice de Graaf. Pavel Kartashev for additional info]