WOOD STONE. 51 
varies according to the direction in which the stone is held to 
the light. 
It is found in pieces that are rounded, massive, or blunt' 
edged. 
These stones are considered by some writers as va- 
rieties of quartz (76), and by others as a kind of opal 
(102). They are sometimes found in Hanover, but 
are chiefly brought from the island of Ceylon. It is 
usual to cut them before they are exported, and ge- 
nerally in a convex and oblong form, without facets, 
and in such manner as to bring the streak which inter- 
sects them into the centre. Among the king of Candy's 
jewels, which were sold by auction in London, in June 
1820, was a cat's-eye of extraordinary magnitude and 
beauty. It was two inches in diameter, of dark colour, 
and nearly hemispherical. This stone was set in gold, 
with small rubies round it, and was sold for more than 
4-00/. 
Cat's-eyes are chiefly used for setting in rings. 
Their size seldom exceeds that of a hazel nut ; but 
there was one in the cabinet of the Dukes of Tuscany, 
which was nearly an inch in diameter. Those that are 
the most highly esteemed are of an olive-green, or red 
colour. 
87. WOODSTONE is a very hard mineral substance, 
supposed to have been wood petrified with a siliceous mineral 
called hornstone. 
It is of various colours; and has not only the external ap- 
pearance, but the internal organization of wood. 
This extraordinary mineral is found embedded in 
sandy loam, in alluvial soil (269), and occurs in various 
parts both of Europe and Asia. It has been found in 
ferruginous sand, near Woburn, in Bedfordshire, and 
near Nutfield, in Surrey. Immense pieces of it are 
discovered in some places in the original shape of the 
trees ; trunks, branches, and roots. In the year 1752 
the whole under part of the trunk of a tree, with its 
branches and roots, was found, in a state of woodstone 
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