456* 



NATURE 



[Sept. 6, 1888 



NOTES ON METEORITES. 1 



II. 



Chemical Analysis. 



^X7E have seen that the main difference between the specimens 

 " * of these bodies which have been collected is that some of 

 them are mainly iron, some of them are mainly stone, and that 

 there is a passage between these two conditions represented by 

 falls in which we have a paste of iron including stony fragments. 



We have now to enter into some points connected with their 

 ■chemical constitution somewhat more in detail. 



Of the chemical elements which are at present recognized 

 as such, about one-fourth are found by chemical analysis to 

 ■exist in meteorites. These, according to the tables given by 

 Maskelyne,- Fletcher, 3 Smith, and others are as follows : — 



Those that occur most constantly are : — 



Hydrogen Carbon 



Iron Oxygen 



Nickel Silicon 



Magnesium Phosphorus 



Cobalt 4 Sulphur ; 



Copper 4 



Manganese 



Calcium 



Aluminium 



-while the following occur less frequently or in smaller 

 quantities : — 



Lithium 



Sodium 



Potassium 



Strontium 



Titanium 



Chromium 



Tin 



Arsenic 

 Antimony 

 Chlorine 

 Nitrogen. 



Of these elementary bodies only hydrogen, nitrogen, and 

 ■carbon occur in an elementary condition. 



Hydrogen and nitrogen are asserted to be occluded as gases 

 by the stones. Carbon exists both in the form of graphite and 

 diamond. 



From the above lists it will be seen that among the elements 

 most common in meteorites are recognized many which have a 

 very wide distribution and exist in great quantities in the surface 

 and envelopes of our planet. But this is true only of the 

 elements. 



Many mineral compounds terrestrially common are absent ; 

 perhaps the most striking case of all is the absolute absence 

 of free quartz, whether crystallized or not, from meteorites, while 

 terrestrially it is the most prevalent compound known, and 

 enters into the composition of such common rocks as trachyte, 

 felsite, syenite, gneiss, and granite. 



Again, many of the chemical combinations met with are un- 

 known to terrestrial mineralogy. The chemical compounds 

 found in meteorites which are new to our mineralogy may be 

 briefly referred to. Some are combinations with sulphur, as 

 follows : — 



Sulphur 



+ Iron 



+ Calcium 

 ( Calcium ) 

 } Titanium \ 



J Iron j 



(^ Chromium J 



+ 



= Troilite 

 — Oldhamite 



= Osbornite 

 = Daubreelite. 



Phosphides of iron and nickel, forming varieties of so-called 

 schreibersite, are met with. 



It has already been stated that carbon in some form or other 

 exists in most meteorites. Some of them are partly composed 

 of this element compounded with hydrogen and oxygen. 



This exists as a white or a yellowish crystallizable matter, soluble 



1 Continued from p. 428. 



2 Nature, vol. xh. p. 505. 



3 " Introduction to Study of Meteorites," p. 30. 



4 With regard to the presence of cobalt and copper, Dr. L. Smith says 

 H" Mineralogy and Chemistry," p. 352): — "In every analysis that I have 

 made of meteoric irons (over one hundred different specimens) cobalt has 

 i>een invariably found, along with a minute quantity of copper." — Flight, 

 " History of Meteorites," p. 164. 



in ether and partly so in alcohol, and exhibiting the characters 

 and the composition of one or more hydrocarbonaceous bodies 

 with high melting-points. 



The meteorites of Alais and Cold Bokkeweld are instances of 

 this group. The former is of a black colour both internally and 

 externally, is combustible, and contains sulphates of magnesium, 

 calcium, sodium, and potassium, which are all soluble in water. 

 The latter, after being experimented upon, left a residue which 

 gave out a very. bituminous smell ; this substance was yellow, 

 and it was found that it was only another form of carbon in 

 a state of intimate mixture, amounting to about 1 '6j per cent. 



Some carbonaceous stones are dark gray in colour, have little 

 lustre, and are soft ; they contain no visible meteoric iron, but 

 an abundance of light gray rounded bodies, among which are 

 occasionally some with a dull metallic lustre and of a greenish- 

 yellow colour, and others of a dark gray compact substance and 

 of earthy character. 1 



Various alloys of nickel and iron also occur. 



The different alloys which play the most important part have, 

 according to Meunier, the following composition : — 



Formula. 



Fe 6 Ni 



Fe 10 Ni 

 Fe 14 Ni 

 Fe 16 Ni 



Among other minerals we may name — 

 Lawrencite, protochloride of iron ; 

 Maskelynite, with the composition of labradorite ; 

 Silica (as asmanite). 



We now come to the common ground. 



The following compounds are identical in composition and 

 crystallographic character with minerals found on our globe : — 



Magnetic pyrites 

 Magnetite 

 Chromite 

 Silicates, viz. — 



Fe 7 S 8 . 

 Fe 3 4 . 



(Fe,Cr) 3 4 . 



Olivine varieties. 

 Enstatite and bronzite. 

 Diopside and augite. 

 Anorthite and labradorite. 

 Breunnerite. 



Among gaseous compounds, the oxides of carbon have been 

 detected in many meteorites, and it is asserted that these gases 

 have been occluded by them in the same manner as the 

 elementary gases hydrogen and nitrogen. 



In the "irons" we deal chiefly with nickel-iron, magnesium, 

 manganese, and copper, as metals. 



In the "stones" we deal with combinations of magnesium, 

 iron, oxygen, and silicon. One of the most usual substances 

 is called olivine, and sometimes the olivine is in a slightly 

 changed form, in which the quantity of iron is increased, 

 and we get bronzite. Nickel-iron, manganese, and other 

 substances are also found in the stones. 



Chemical analysis of the irons has established in them, taken 

 as a whole, the existence of the following mineral species. 



(1) The general metallic mass, which consists of certain alloys, 

 in which iron and nickel predominate to such an extent that the 

 term nickel-iron is by common consent applied to it. 



The nickel-iron is an alloy or compound special to meteorites, 

 and the irons are chiefly composed of it. The tracery to which 

 I have referred, observed on the metallic surface heated with 

 acids, was discovered by Widmanstatten. The figures are 

 caused by the crystallization of the mass : with the iron and 

 nickel magnesium is always associated, so that zve get magnesium 

 in all meteoric irons as well as in the stones. 



(2) Compounds of iron and carbon, principally campbelline 

 and chalypite (Fe. 2 C). 



(3) Troilite (FeNi) 7 S 8 , generally appearing as kidney-shaped 

 masses. 



(4) Schreibersite (Fe 4 Ni 2 P). 



(5) Graphite. 



(6) Stony grains, generally magnesium and iron silicates. 



(7) Occluded gases. 



1 Flight, 0/. at. p. 2ii. 



