196 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxiv. 
made out. It is colorless, polarizes in light and dark shades only, 
shows no satisfactory crystal outlines or cleavage, and in but one 
instance was I able to get what was apparently one of the bars of a 
biaxial interference figure. They are perhaps feldspathic. Their 
small size (the entire aggregate in fig. 6 being onlj^ some four-tenths 
of a millimeter in diameter) renders their separation for microchemical 
tests practically impossible. 
Others of these areas are so finely cryptocrystalline and merge sa 
gradually into the ground mass that it is scarcely possible to consider 
them as mechanically included fragments. 
The chemical composition of the stone is shown in the analyses given 
below, as made in the laboratory of the department by Dr. Peter 
Fireman. 
By treatment with solution of the double salt of mercuric ammonium 
chloride, after the method of Carl Friedheim,^ there was obtained: 
Per cent. 
(«) Metallic portion 3. 04 
[b) Nonmetallic portion (inclnding troilite and chromite) 96. 96 
100.00 
The metallic portion 3nelded: 
Per cent. 
Fe '. 85. 04 
Ni 11. 93 
Co 2. 79 
Cu 0. 24 
100. 00 
The silicate portion was digested with hydrochloric acid and sodium 
carbonate solution after the usual method. The soluble and insoluble 
portions then yielded results as below, deducting those constituents 
present in combination, as troilite, chromite, or as free carbon. 
Soluble silicate. 
Per cent. 
SiO, 32. 91 
AL63 2. 73 
Feb 34. 74 
MnO - 0. 94 
NiO & CoO 1. 39 
CaO 6. 43 
MgO 19. 39 
K.O ■ 0. 11 
Na.O 0. 70 
H.,0 at 110° 0. 22 
99.56 
Insoluble silicate. 
Per cent. 
SiO, 53. 59 
Al^Og 6. 97 
FeO 3. 50 
CaO 4. 33 
MgO 31. 33 
K2O 0. 34 
JSfaoO 0. 63 
100. 69 
^ Sitz. d. k. Preuss. Akad. der Wissenschaft 1888, p. 345. 
