THE YOUNa 
SCIENTIST. 
(!) or barberries ; green with a mixture of 
three i^arts verdigris and one part sal- 
ammoniac dissolved in vinegar; and a 
fine blue by steeping them alternately in 
the above green bath and in potash lye. 
Black is obtained by alternate baths of 
logwood and black liquor —Moniteur de 
la Teinture. 
Gems and Precious Stones. 
GEMS and precious stones always excite 
interest, not only from their great 
value, but on account of their exceeding 
l)eauty and the deep scientific interest 
which attaches to them. It is a wonderful 
fact that the diamond has almost exactly 
the same chemical constitution as the 
black lead which we use in our pencils, 
and the ruby and sapphire are merely 
pure alumina — an earth which forms a 
very large proportion of the soil which we 
till, and which, w^hen out of place, we call 
"dirt. A few words in regard to the prin- 
<?ipal gems may therefore please our 
young readers. 
The Diamond is the hardest known sub- 
stance, and one of the most unalterable 
gems. It is not affected by chemicals, is 
infusible, only to be consumed by exposure 
to a long-continued or very high tem^Dera- 
ture ; and these qualities, combined with 
its rare brilliancy, make it the most valu- 
able of precious stones. It is pure car- 
bon ; chemically almost the same as 
graphite, or plumbago, and charcoal ; 
but very different from them in its trans- 
parency and lustre. It is generally found 
in octahedral crystals, having highly pol- 
ished faces; and although possessing 
some beauty in this natural state, owing 
to the high lustre of the faces, yet it has 
not a tithe of the splendor exhibited by a 
well-cut brilliant. The ancients did not 
know how to cut the extremely hard dia- 
mond, and were content to wear it in its 
natural state, but even thus they prized it 
highly. 
According to their transparency and 
lustre, diamonds are classified into stones 
of the first water, second water, and refuse 
stones. To be the first water a diamond 
must be absolutely colorless, very lus- 
trous, and perfectly free from flaws. An 
undecided tint of any color injures its 
value ; and although deep red, green, or ! 
blue hues may give the stones an excep- i 
tional value as fancy specimens, yet in the ; 
ordinary market they would be much less 
esteemed. A yellow tint always depre- 
ciates the value; and on this account 
many of the stones so recently found in i 
South Africa bring very low prices. These 
African stones, moreover, lack the perfect 
lustre of Brazilian diamonds, and have, in 
consequence, commanded far lower prices. 
A well-cut diamond, of the first water, 
is at present worth in New York about $50 
gold, if it weighs half a carat (the carat • 
being four grains Troy) ; if weighing one 
carat, $175 ; if two carats, $550. Above this | 
weight the values depend on very delicate [ 
shades of difference. One stone of three I 
carats may bring $800, another might be | 
worth $1,000. Above three carats the price | 
is only settled by agreement. A diamond ! 
of five carats is a very large stone, and 
above one hundred carats few are known. 
Diamonds are found in alluvial deposits, 
from which they are separated by wash- 
ing. In Brazil the work is done by slaves, 
and the fortunate finder of a stone of over 
seventeen carats receives his freedom and I 
a suit of clothes. Scarcely one in ten 
thousand is found to weigh so much, and 
the majority of them weigh but a very 
small fraction of a carat. 
The most celebrated localities in ancient 
times were Golconda and Borneo ; but in | 
1727 the diggings in Brazil vjere opened, 
and yielded so abundantly as to greatly 
depreciate the value of diamonds, and the 
dealers tried to make people believe that 
they were not true diamonds. Lately 
diamonds have been found in Australia 
and South Africa, and a few in North 
Carolina, Virginia, and California; but 
Brazil furnishes the most abundant sup- 
plies and the best gems. 
In our next article we shall tell our 
readers something about rubies and sap- 
phires. ^ ^ ^ 
— The best rock-work for aquaria might 
be made of clay, such as is used for terra 
cotta, moulded to the required form, and 
baked quite hard, but not glazed. It j 
might be colored of any tint before being 
baked. 
