Dr. Davy on the Geology and Mineralogy of Ceylon. 321 
common zircon and hyacinth, I have met with a third, massive, 
opaque, and uncrystallized, and of a dark brown colour. I have 
specimens of it weighing two or three ounces from Saffragam. I 
may notice another mineral from the same part of the country, 
which appears to me to belong to this family ; it is black, opaque, 
of small conchoidal fracture, and vitro-resinous lustre, hard, of high 
specific gravity, in general amorphous, rarely crystallized, the crystals 
imperfectly formed four-sided prisms terminated by four-sided py- 
ramids ; I describe from memory, my specimens being at Colombo. 
The natives, I need not say, are completely ignorant of the true 
nature of zircon : the yellow varieties are sold as a peculiar kind of 
topaz ; the green as tourmaline ; the hyacinth red as ruby ; and the 
very light grey as diamonds. All the varieties that are brought into 
the market are found in the beds of rivers, or in alluvial ground. 
Both in Saffragam and Matura the nature of the alluvion is the 
same ; it is derived from the decomposition of gneiss rock. Near 
the fort of Matura, where I saw several specimens of this mineral 
found, the alluvion consisted of quartz and clay, with mica and 
graphite, and some other minerals disseminated through it. The 
only places where I have discovered zircon in its natural situation, 
are, a small island in Belligam bay belonging to the district of 
Matura, and a few miles from Belligam, on the way to Galla. On 
the former spot, it is sparingly disseminated through a rock consist- 
ing chiefly of quartz and schorl. At the latter it occurs abundantly 
in a rock composed of quartz and adularia : the zircon in some 
parts of the mass is in so large a proportion, that the rock almost 
deserves the name of the zircon rock. The mineral in this instance 
is crystalline, and most commonly green or brown ; the rock is re- 
markable for its specific gravity and the resinous lustre of its frac- 
ture. 
2 s 2 
