GEMS AND PRECIOUS STONES OF GREAT BRITAIN. 
133 
British jet is still much used for personal ornament in Eng- 
land ; it is chiefly obtained from the liassic strata near Whitby, 
Yorkshire, where it occurs imbedded in various-sized pieces, 
due to the subsequent bituminisation and change of coniferous 
wood, which was entombed in the sea-mud of that period. 
Amber, or the fossil resin of coniferous trees, has been fre- 
quently found on the east coast of Britain, although the chief 
source of supply is from the southern coast of tbe Baltic, derived 
from the tertiary strata of that district. 
It appears accordingly to have formed one of the most 
favourite articles for adorning and setting brooches, hair-pins, 
and other personal ornaments, from the earliest practice of the 
jeweller’s art, until our native tastes and customs were merged, 
by increasing intercourse with other nations, into the common 
characteristics of later mediaeval art.” * 
Table of Physical Characters of Gems. 
Colourless 
Red I 
Yellow 
Green 
Blue 
Violet 
Brown 
Black 
Hardness 
Spec. Gray. 
Scratches 
Refraction 
Electric 
Quartz 
Glass 
By 
Heat 
By 
Friction 
Diamond . . 
X 
X 
X 
X 
X 
X 
X 
10 
3-5 
X X 
X 
St 
Sapphire . . 
X 
X 
X 
X 
X 
X 
9 
3-9-4 
X 
X 
D 
X 
Chrysoberyl . 
X 
X 
8-5 
3-7 
X 
X 
D 
Spinel . . . 
X 
X 
X 
X 
8 
3-7 
X 
X 
S 
X 
Topaz . . . 
X 
X 
X 
X 
8 
3-5 
X 
X 
D 
X 
Zircon . . . 
X 
X 
X 
X 
X 
7-5 
4-6 
X 
X 
D 
Beryl . . . 
X 
X 
X 
? 
7-5 
2-6 
X 
X 
D 
Emerald . . 
X 
X 
7-5 
2"6 
X 
X 
D 
Rock Crystal 
X 
X 
X 
7 
2-6 
X 
D 
X 
Amethyst . . 
X 
7 
2-7 
X 
D 
X 
Chrysolite. . 
X 
6-7 
3-4 
X 
D 
X 
Garnet . . . 
X 
X 
X 
X 
X 
6-7 
3-8 
? 
X 
S 
Tourmaline . 
X 
X 
X 
X 
X 
X 
6-5 
3 
? 
X 
D 
X 
Turquoise . . 
X 
X 
6 
2-6-3 
X 
Lapis lazuli . 
X 
5-5 
2-4 
? 
Opal . . . 
X 
X 
X 
X 
6 
2-3 
? 
Malachite . . 
X 
3-5-4 
3-9 
0 
* D. Wilson : Archaeology and Prehistoric Annals of Scotland,” p. 305. 
t S. Single. D. Double. 
Note. — Some of the specimens figured on the Plate have been kindly lent 
by Mr. J. Gregory and Prof. Tennant. 
