  Major element fractionation among chondrites has been discussed for decades
as ratios relative to Si or Mg. Recently, by expressing ratios relative to Fe,
I discovered a new relationship admitting the possibility that ordinary
chondrite meteorites are derived from two components, a relatively oxidized and
undifferentiated, primitive component and a somewhat differentiated, planetary
component, with oxidation state like the highly reduced enstatite chondrites,
which I suggested was identical to Mercury's complement of lost elements. Here,
on the basis of that relationship, I derive expressions, as a function of the
mass of planet Mercury and the mass of its core, to estimate the mass of
Mercury's lost elements, the mass of Mercury's alloy and rock protoplanetary
core, and the mass of Mercury's gaseous protoplanet. Although Mercury's mass is
well known, its core mass is not, being widely believed to be in the range of
70-80 percent of the planet mass. For a core mass of 75 percent, the mass of
Mercury's lost elements is about 1.32 times the mass of Mercury, the mass of
the alloy and rock protoplanetary core is about 2.32 times the mass of Mercury,
and the mass of the gaseous protoplanet of Mercury is about 700 times the mass
of Mercury. Circumstantial evidence is presented in support of the supposition
that Mercury's lost elements is identical to the planetary component of
ordinary chondrite formation.
