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THE RUBY. 145
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exposed
to continuous daylight; whilst the other was enclosed in a sealed box
from which all light was carefully excluded. The stone kept in
daylight had lost a distinguishable amount of colour after a few years
when compared with the other stone which had been kept perpetually in
darkness; and thereby the former stone had lost some of its value.
The
Balas Ruby, or Spinel, is of a fine, lively, red colour, but has a
common tint intermixed, which renders it far less brilliant than the
true Ruby, or Red Sapphire. In chemical composition the Spinel contains
one molecule of alumina, and one of magnesia ; or, in one hundred
parts,—of alumina seventy-two, and of magnesia twenty-eight. This stone
does not exhibit electricity, either by friction, or by heat. During
trie-Middle Ages the same supernatural powers were attributed thereto
as to the true Ruby. Elianus, an ancient author, who wrote a Natural History of Animals, relates
that a Stork once presented a woman named Heraclis with one of these
stones, the bird thus showing its gratitude for her kindness to it in
curing a broken leg. The colour of a Spinel will generally become
deeper, and intensified if it is carefully heated. " The Balas," said
Boetius, De Natura Gemmarum, " restrains passion and fiery
wrath, and is a preservative from lightning." As already stated, the
true Ruby—a red variety of Corundum—is of great rarity and value ;
whilst the Spinel, an aluminate of magnesium, is inferior in hardness,
and much less esteemed as a Gem. The test of a perfect Ruby is its
exact agreement in colour with the fresh blood of a pigeon, dropped
upon the same sheet of paper immediately next the stone.
Ine Tourmaline—which sometimes goes by the name
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