METEORITES CONDUCTIVITY CHART, page 3
Chart of Conductivities of Iron Spheres, Iron Pieces and Meteorites of Same Size
The Iron and Stony Iron types of meteorites contain iron with various amounts of nickel which greatly reduces the conductivity of metal alloy in meteorite. To show the difference between iron meteorite's conductivity and conductivity of an iron piece of the same size, an experienced meteorite hunter Roberth Hoolko created the chart shown below.
The chart illustrates the relationship between the V.D.I. numbers and the sizes of iron spheres, iron pieces and meteorites. To create this chart, first, Roberth made many iron spheres of different sizes and measured their diameters. Then he scanned each sphere with a search coil, got the V.D.I. reading and placed it against the sphere's corresponding diameter on the chart. After repeating this procedure with all iron spheres, Robert could draw a perfect line (red dotted line on a chart) showing the relationship between the V.D.I. numbers and diameters of spheres.
Then he took two dozens of compact iron pieces of different sizes and scanned each piece with a search coil from three different directions. After he got three V.D.I. readings for each piece, Robert calculated the average V.D.I. number and placed it on the chart where this number would correspond to the piece's size. As it shows on the chart, all the resulting orange points lay very close to the red dotted line.
When Robert conducted the same procedure with meteorites, the resulting blue points lay far from the red dotted line. This clearly showed the influence of the meteorites' nickel content on their conductivity. An iron piece and a meteorite of twice the size of iron piece would share the same conductivity number.