this
stone is highly prized when found without spots, being very subject to
defects, so that it is often diminished in value by having a violet
tint, clouded with a black shadow, or deadened by a wax tint which
whitens it too much."
"
The best colour for this stone is clear, neither too much dulled by a
dark tint, nor too light by excessive transparence, but inclining to a
medium colour between blue and purple. This is the gem which is
sensitive to the air and sympathises with the heavens, and which does
not shine equally whether the firmament is dark or light. Besides this,
when put in the mouth, it is colder to the taste than other gems. As to
being engraved, it is not very suitable, because not easily cut
(attritum respuat) : nevertheless, it is not altogether invincible, as
it may be cut and engraved in different forms (scribitur et figuratur)
by the diamond."
From all these descriptions, it appears certain to me that the ancients applied the term sapphirus to some blue stone, like that which we now call zappherine. Besides, they denoted specially under the name of sapphirus that particular stone called by us lapis-lazuli. And that, finally, they gave the name of hyacinthus, without any doubt, to that precious substance now called by us corundum, because
in its various forms it is like the different colours of the flower
into which Hyacinth, the young friend of Apollo, was changed. And
therefore they called the ruby corundum hyacinthus purpureus, and the blue corundum hyacinthus sapphireus.
