14 
THE HALL. 
which exhibit, by transmitted light, an internal zoned structure 
of singular regularity. 
The following case (No. IV.) is devoted to the natural forms of 
silica, including the species quartz and opal, the latter being for 
the most part a hydrated form of silica. Here will be found 
excellent examples of all the typical forms of quartz, such as 
rock-crystal, amethyst, and other siliceous minerals, some of 
which are strikingly beautiful in colour. A larger collection of 
such minerals may, however, be studied on the floor above. 
(See p. 111.) 
The succeeding case (No. V.) is filled with a collection of 
Native Oxides. Ferric oxide forms a large series, including 
some magnificent crystals of specular iron-ore from Elba, 
remarkable for brilliancy of lustre, and in some cases for 
iridescence. The “ rosettes,” or aggregates of hexagonal plates, 
are characteristic of the specular iron of St. Gothard. Mag - 
netite, or magnetic oxide of iron, is represented by some sharp 
crystals, mostly octahedra, and by a sample of “ natural load- 
stone,” bristling with the iron filings which it has attracted to 
its surface. Students of mineralogy will appreciate the 
splendid crystals of brookite, from North Wales, and of anatase 
from Dauphine, which are here placed with, the rutile, all three 
minerals consisting of oxide of titanium. Cassiterite, the chief 
ore of tin, is represented by a suite of crystals of singular 
beauty, many of them twinned, from the old tin mines of 
Cornwall, Saxony, and Bohemia. 
The last case (No. VI.) contains selected specimens of Native 
Carbonates, commencing with some fine crystals of cerussite, or 
lead carbonate, known also as “ white lead ore.” Those are 
followed by a handsome series of the hydrated carbonates of 
copper, the green being known as malachite and the blue as 
chessylite : the former are chiefly from Siberia and Australia, 
the latter from Chessy, near Lyons, in France. Succeeding these 
are numerous specimens of ferrous carbonate, termed by 
mineralogists siderite and chalybite. Specialists will admire 
the specimens from Wheal Maudlin, in Cornwall, showing in 
perfection the zoned structure so characteristic of this locality. 
The case contains also some interesting examples of the carbonate 
of zinc, generally called calamine , principally from Vieille 
Montagne, between Belgium and Rhenish Prussia. 
A wall-case, forming part of one of the Ludlam cabinets, 
standing on the western side between the pilasters numbered 
139 and 142, has recently been fitted up, temporarily, with a 
selection of fine specimens from the groups of phosphates , 
arsenates and sulphates. 
Each specimen in the Ludlam collection is distinctly labelled, 
and further information may be obtained on reference to the 
names of the several minerals in the Index at the end of this 
Handbook. 
