SELBORNE SOCIETY NOTICES 
70 
Ranking next the diamond in value comes corundum, which seems able to 
assume any colour. It may be quite clear and resemble the diamond except in 
a lesser degree of hardness ; or yellow when it is known as topaz. Originally 
“topaz” meant a yellow stone, but as yellow stones are numerous the word 
“ oiiental ” is prefixed to show its superiority to every other kind of yellow stone. 
Again, corundum may take a hlue tint and prorluce a sapphire ; or red and 
beconre a ruby ; green and rank as an emerald ; or purple and be known as 
an amethyst; but to distinguish the corundum gems from all other precious 
stones of similar colours the word “ oriental ” Ls again used — oriental emerald, 
oriental sapphire, &c. Corundum with the tint of “ pigeon’s blood ” is the rarest 
and most treasured. Crystallisation in these stones brings out the structure, and 
in a strong light a silvery six-rayed star may be seen, which gives the name 
“ star stones ” to these gems. 
All precious stones, except the diamond, are formed of compounds of diflferent 
elements, and yet one stone may be identical with another in composition, 
but entirely different in appearance and structure. The alexandrite and oriental 
chrysolite, for example, have the same chemical composition and yet they are 
totally unlike each other to look at, for the former is very dark-green by 
daylight and red by artificial light, while the latter is simply a greenish-yellow 
by both lights. 
Spinel is softer than corundum, but it ranges through an iris of colouring. Its 
red and rose-tinted varieties are the spinel and balas rubies, used as pivots for 
the wheels of watches. 
Quartz, when clear, is the Brazilian pebble of the spectacle-maker. Some 
quartz crystals seem of a very friendly disposition, and take into their hearts fine 
needles of other minerals. One quartz crystal exhibited has its “ ghost ” always 
on view. After the crystal was formed another started to grow in its interior and 
the result is truly ghostly. 
Other quartz crystals hold in their stony thraldom water and bubbles of air, 
and this, together with the fact that casts of shells are found consisting of pure 
quartz and chalcedony, tells that the mineral matter must have been deposited at 
first in liquid form. 
From the smoky varieties of quartz we get the cairngorm and occidental 
topaz, whilst the violet amethyst is distinguished from all other varieties of quartz 
by its rippled fracture. Opal is formed from a combination of silica and water. 
Sometimes, however, these two substances refuse to crystallize, and it would seem 
that in the struggle to depart from the ordinary routine fractures occur, which in 
the end give that delightful play of colour for which opals are so famous, for opals 
are merely' an amorphous form of silica combined with water. The fire opal 
from Mexico is especially beautiful in its caprice of colours, which range from 
honey-yellow to flaming hyacinth-red. 
One of the most valued of precious stones is the emerald, a bright-green 
variety of beryl. Emeralds are full of flaws and cracks, so that a large and 
perfect specimen is very rare. When the stone is colourless it retains the name of 
beryl, when bluish-green it is known as aquamarine. 
A variety of precious stone, emerald-green in colour, to which the name 
“ Hiddenite ” has been given, was discovered in rather a strange way. An 
emerald mine in North Carolina yielded but one emerald. However, during the 
working another kind of stone was found, almost identical in colour, but entirely 
different in composition, which has never before or since been found anywhere 
else. Specimens of artificially-coloured agate exhibited are very interesting. For 
many years the agate industry was carried on at Oberstein, on the banks of the 
Rhine. In time all the available material became exhausted, and to fill its place 
agate was brought from America as ballast. Some layers of agate, it appears, are 
porous and some are not. The stones are boiled in colours, and the porous bands 
take in the stain while the denser ones refuse it. The result shows tinted bands 
alternating with white, as in the natural specimens. 
Tourmalines are of almost every conceivable colour, and among them is found 
the interesting occurrence of a green outer crystal enclosing a red one. Tourma- 
line reminds one of some of Culpepper’s herbal prescriptions, where a little of 
everything comes in. Indeed, it seems almost easier to say what elements 
tourmaline does not consist of than what it does. Black tourmaline is in great 
request for mourning jewellery. 
