222 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
TaBiE III.—Composition of the principal precious stones. 
Species. Variety. Composition. 
Element........ Diamond sesee | bee eee ese eee ne eee aces Carbon. 
RUD Yee oee eee ae soon 
Corundum.... {snr MSIF. F32b.3.285 joss of aluminium. 
OGae so | Oriental amethyst, etc.. 
Crystal cscsmcisecsi2 go -!=5 
Quartz. - tees AMOCUY Suse sce eee aes aes fe 
Cairngorm, etc.......--- 
nie Spinel.--t-<-> Balas'ruby, etce:..:....-- Maguesium aluminate. 
uminates...-- 
seat ae ation : i ; : : : é ; ‘ | Beryitium aluminate. 
Beryleencence- eee ei Beagtitnoer ae |Berynium aluminium silicate. 
Aquamarine. ..........- 
Hessonite: on.so-5)--)5-cc Calcium aluminium silicate. 
Coach aie IAB een nob deiioSscic Magnesium aluminium silicate. 
Almandine 2 es. 222493 Tron aluminium silicate. 
Demantoid, etc......... Calcium iron silicate. 
Silicates sss. Olivene......- (Peridot) ess ssesesccene Magnesium iron silicate. 
SPHENCS eeecc| eee cre see eect eee coe Calcium titanium silicate. 
Spodumene...| (Kunzite).........-....- Lithium aluminium silicate. 
i Noy oRY Pee ece we) Woe Bem ce Hae ameter Sea Aluminium fluo-silicate. 
(ounmaline sess cen: sconce aa eeasecncre Complex alkali-lime-alumina silicate. 
(iteom...----ivacintin, | ireomiam siteat. 
Murquoises OSs yshs- beast vat csc besos se Hydrous aluminium phosphate. 
O pales see es| Stee adene ee eta nese ae Hydrous silica. 
Pearle. Sickeees|aseccoosse ce cet oes See e eee Calcium carbonate. 
The most important point to remember about paste, however, is 
its lack of durability; it is not only too soft to stand much wear, butits 
composition is so unstable that it rapidly deteriorates and loses its 
brilliancy on exposure. You will see, therefore, that although there 
is a certain legitimate scope for such paste imitations they are very 
unsatisfactory substitutes for the genuine article. This being the 
case, as scientific knowledge has advanced, attention has been more 
and more concentrated on the problem of producing by artificial 
means the actual minerals found in nature, and thus obtaining what 
I have defined as artificial in contradistinction to imitation jewels, 
having both the beauty and durability of the natural article without 
the objectional concomitant of enormous cost. 
The first point to be considered in attacking this problem is the 
composition of the stone, as it is obvious that, other things being 
equal, the possibilities of success are greater with one of simple than 
one of comparatively complicated composition. One also has to 
consider, however, the economic aspect—it is not much use devoting 
time and ingenuity to the production of an artificial stone when the 
natural one is so common that the cost of the two would be practically 
identical. 
