Gem Stones and Their Characteristics
| Author | F. E. Ullmann |
| DOI | 10.1177/0032258X4301600114 |
| Published date | 01 January 1943 |
| Date | 01 January 1943 |
| Subject Matter | Article |
Gem Stones and their Characteristics
By F. E. ULLMANN, F.G.A.*
Values
Valuable
Not
so 'valuable
Extremely
valuable
Colours
Usually colourless
Often
yellowish or
brown
Sometimes,
but
rarely, pale
green,
blue
or
pink
Blood
red
Very valuable
All shades of
blue--cornflower
Very
valuable
and
royal
blue
Blue black
and
very
pale
blue
Not
valuable
Pink,
yellow,
dark
green,
Of
no very
great
colourless value
(None
of
these
colours is
obtained
by
heat
treatment)
CORUNDUM
Ruby
Sapphire
IT was with great interest that Irecently read " Hints on describing
jewelled
articles"
in THE
POLICE
JOURNAL
of january 1938 (Vol. XI,
No. I), and although somewhat belated Ifeel it may be useful to correct
one or two slips which occur in that most informative description of
jewellery from a police officer's point of view.
A good generalisation is to term most stones mounted in jewellery
of any worth " gem stones."
The
classification into " precious " and
"semi-precious" stones is at best only an arbitrary division and is in
any case misleading. Many of the so-called semi-precious stones are
of far greater value and rarity than the traditional precious stones.
To
quote
but
one of many examples, several varieties of garnet are most
uncommon and when found fetch very high prices indeed.
.Without probing too deeply into the science of mineralogy, Ithink
the following points are worthy of note.
The
great majority of gem
stones are crystalline substances and when in their natural state are
found either as crystals or water-worn pebbles. Most crystals, when
chemically pure, are colourless, so that the majority of gem stones
derive their colours from minute traces of metallic oxides (impurities)
which are introduced into the stone during the process of formation
in the earth's crust.
The
correct classification of gem stones is by their mineral species,
which, in their turn, are often divided into varieties.
The
variety name
is then sometimes designated to an appropriate colour.
The
following list gives the specific names of minerals most
commonly used as gem stones, together with some of their variety
names and colours. An indication of their relative values is also shown:
Species Varieties
DIAMOND
None
*
Mr.
Ullmann,
who is at
present
asergeant in the
Metropolitan
Special
Constab-
ulary, is a specialist in pearls
and
precious stones.
He
was
the
managing
director of
afamous
Bond
Street
firm of jewellers. 56
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