Theralite
“Nepheline gabbro from alkaline depths”
Theralite is a coarse-grained alkaline igneous rock essentially composed of plagioclase, nepheline, and clinopyroxene — think of it as a gabbro where nepheline replaces the usual quartz. It occurs in alkaline intrusive complexes, often alongside ijolite and nepheline syenite.
plagioclase (labradorite), nepheline, augite (titaniferous), olivine, biotite, magnetite
Pilansberg Complex (South Africa), Alnö (Sweden), Cripple Creek (Colorado, USA), Kola Peninsula (Russia), Kaiserstuhl (Germany)
5.5-6
The Pilansberg Complex in South Africa, where theralite is found, is the eroded root of a 1.2-billion-year-old volcano that's now home to a national park where visitors can see ancient alkaline rocks alongside roaming wildlife.
Test Your Knowledge
Theralite is essentially a variety of gabbro where nepheline replaces which mineral normally found in standard gabbro?
Related Specimens
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