Using Ive's SpectralRender, I get strange colors for chrome and gold.
M_Chrome() renders a dark navy blue, and M_Gold() renders a pure yellow that
seems much too garish.  I'm sure the little bit of gold I've seen in person is
only 14 kt, but the images of pure gold I've seen are less saturated and have an
orange cast.

Using C_Metal in preview mode yields rgb <0.5496, 0.5559, 0.5549> for chrome and
rgb <1.0224, 0.7810, 0.3449> for gold, which are much more the colors I expect.
However, M_Chrome() and M_Gold() in preview mode yield smoky black and silvery
white, respectively.

The following scene description file illustrates the anomalies:
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#version 3.7;
#include "spectral.inc"

#ifndef (Rad) #declare Rad = yes; #end
global_settings
{ assumed_gamma 1
  max_trace_level 15
  #if (Rad)
    radiosity
    { count 100
      error_bound 0.5
      pretrace_end 2 / image_width
      pretrace_start 32 / image_width
      recursion_limit 2
    }
  #end
}
camera
{ location <0.0, 1.25, -7.0891>
  look_at <0.0, 1.25, 0.0>
  angle 38.8508
}
light_source
{ <-3.6875, 8.6250, -6.3869>,
  SpectralEmission (E_D65) * 5013.1
  fade_power 2 fade_distance 0.10417
  spotlight point_at <0.0, 1.25, 0.0> radius 45 falloff 90
}
#default { finish { diffuse 1 ambient SpectralEmission (E_D65) * 0.24520 } }
box
{ -1, 1 scale <9, 10, 9>
  pigment { rgb 0.6 }
}
plane
{ y, 0
  pigment { checker rgb 0.03 rgb 0.6 }
}

sphere
{ <-1.2, 1, 0>, 1
  M_Chrome (1)
}
sphere
{ <1.2, 1, 0>, 1
  M_Gold (1)
}
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