Note 1 — Chapter XI

Isolated masses of native iron are usually of meteoric origin, but to determine whether or not the native iron fell from the sky a portion of the surface is ground off and polished; then the polished surface is etched with acid. If crystalline lines are plainly brought out, there can be no doubt of its being of meteoric origin.

The following excerpt from the American Museum Meteoric Guide will make the matter clear: "The iron of meteorites is always alloyed with from six to twenty per cent of nickel. This 'nickel-iron,' as it is commonly called, is usually crystalline in texture, and when it is cut, polished, and 'etched' a beautiful net-work of lines is brought out, indicating plates which lie in positions determined by the crystalline character of the mass. This net-work of lines constitutes what are called the Widmannstattian figures, from the name of their discoverer. When these figures are strongly developed the meteoric origin of the iron cannot be questioned, but their absence does not necessarily disprove such an origin. Native iron of terrestrial origin is extremely rare."