

THE COLLECTION OF MINERALS 
when one considers the fact that Mr. Bement, a collector of rare judg- 
ment and appreciation, not infrequently purchased an entire small 
collection in order to acquire a single specimen of unique value. Since 
the gift of the Bement Collection many additions of exceptional beauty 
and interest have been acquired by purchase from the Fund estab- 
lished in 1904 by Matilda W. Bruce. The Mineral Collection which 
thus attained a high standard of merit has been augmented year by 
year through careful selection of the best available specimens of the 
more recently discovered species, varieties and occurrences. The more 
newly acquired of these will be found in the small cases of Recent 
Accessions displayed at the entrance of the Hall. 
CLASSIFICATION OF MINERALS 
A mineral is a natural chemical compound, that is, it has in most 
instances a definite chemical composition, and it is this chemical composi- 
tion, constituting as it does the essential and unvarying characteristic 
of a mineral, which forms the basis of its classification. There are many 
thousands of compounds known to chemists which include the 800 or 
more natural compounds, or minerals. But all of these when reduced 
to their simplest constituents are proved to be made up from combina- 
tions of a relatively small group of ultimate substances called elements. 
Of the 80 or more elements at present known, there are 20 which 
are so common that they make up 99% percent of the surface layer of 
the earth’s crust to a depth of 10 miles, which marks the limit of our 
knowledge, and of these 20 only 8 are needed to constitute 97 percent of 
this surface layer. The 20 commonest elements in the order of their 
abundance are: 
1. Oxygen O 5. Calcium Ca 
2. Silicon Si 6. Potassium K 
3. Aluminum Al 7. Sodium Na 
4. Iron Fe 8. Magnesium Mg 
These constitute 97 per cent 
9. Titanium Ti 15. Manganese Mn 
10. Hydrogen H 16. Chlorine Cl 
11. Carbon C 17. Strontium Sr 
12. Phosphorus P 18. Fluorine Fl 
13. Sulphur S 19. Zirconium Zr 
14. Barium Ba 20. Nickel Ni 

