Mesocratic rocks fall in the middle of a 100-point index of this property. For 10 points each:
[10m] Name this property that is especially variable in tourmaline. A cylindrical coordinate system used to describe this property for soil was developed by Albert Munsell.
ANSWER: color [accept color index]
[10h] Rocks that are holomelanocratic in color index correspond mineralogically to this classification. QAPF diagrams are replaced by ternary diagrams measuring olivine and two pyroxenites for rocks of this type.
ANSWER: ultramafic [accept ultrabasic; accept descriptions like being composed of mostly mafic minerals or entirely mafic; prompt on mafic alone]
[10e] Due to their low silica content, ultramafic rocks generally lack this first mineral in the QAPF classification. Color distinguishes varieties of this silicon dioxide-composed mineral like amethyst and a “rose” type.
ANSWER: quartz [accept rose quartz]
<Jeremy Cummings, Other Science>