THE CAROLINE STONY METEORITE 
43 
grain-size is, however, variable. Many of the olivine crystals 
are iron-stained and some contain clusters of minute opaque 
inclusions some of which proved, in reflected light, to be 
nickel-iron and pyrrhotite. 
Occasionally very minute particles of reddish brown iso- 
tropic chromite form inclusions in both pyroxene and olivine. 
Small irregular plates of merrillite (1), a sodium calcium 
phosphate, occur interstitially between crystals of olivine 
and pyroxene. These plates are clear and colourless and 
have very low polarization colours; they are uniaxial and 
negative, with a refractive index a little lower than that of 
olivine. Merrillite is attacked by dilute nitric acid, and when 
a little powdered meteorite, from which the more highly 
magnetic fraction has been extracted (the bulk of the powder 
can be lifted by a strong magnet), is treated with dilute nitric 
acid for five minutes, the solution gives reactions for both 
calcium and phosphorus. These tests do not distinguish 
between phosphorus derived from merrillite and phosphorus 
derived from oxidized nickel-iron. Dr. A. B. Edwards 
determined the amount of P 2 O 5 extracted in this way to be 
0 21 per cent., and the total amount of P2O5 in the fraction 
to be 0 48 per cent. Occasional small, clear, interstitial 
particles of low refraction and birefringence are attributed 
to felspar; they are biaxial and positive, sometimes show 
cleavage and one shows traces of lamellar twinning. A 
green secondary mineral in one of the limonite veins is either 
a chloritic or serpentinous decomposition product of the 
silicates. Another vein of limonite has a core of undeter- 
mined clear, colourless, secondary mineral with a low 
refractive index and very low birefringence. 
Examination in Reflected Light. 
Primary minerals recognizable on polished surfaces of 
the meteorite include small grains of nickel-iron, pyrrhotite 
and chromite disseminated among the silicates; in addition, 
trevorite and limonite, are present as products of weathering. 
Nickel-Iron. The largest grain of nickel-iron measures 
0 43 X 0 23 mm. and is comparable in grain-size with the 
olivine. Oxidation of nickel-iron has progressed inwards 
from the surface and, when incomplete, a core with a corroded 
outline is surrounded by limonite ; grains initially large may 
be represented by one or more particles of nickel-iron in a 
large area of limonite (Fig. 1) ; some small particles of nickel- 
iron, however, have a mere thin rim of limonite, and a few are 
