Varieties of these orthorhombic minerals include tephroite and knebelite.
Varieties of these orthorhombic minerals include tephroite and knebelite. The magnesium-rich  variety of these minerals is believed to be the most abundant(*) consitutent of the upper mantle. These mafic minerals crystalize first in the continuous part of Bowen's reaction series, and its varieties include forsterite, also known as peridot. For 10 points— identify this group of minerals which gets its name from the green color of its magnesium-iron series.
Varieties of these orthorhombic minerals include tephroite and knebelite.
olivine