NON-METALLIC MINERALS. 
1U7 
Is manufactured from the brine springs of Cheshire and 
Worcestershire, which rise from beds of Rock Salt. : The rock salt 
itself is largely worked at North wich, in the valley of the 
Weaver, and near Belfast, in Ireland. A thick bed has been 
found at a considerable depth at Middiesbro’-on-Tees. The rock 
salt of Cheshire occurs, associated with gypsum, near the base ol 
the New Red or Keuper Marl. Occasionally the salt is colourless 
and crystalline, but usually it is coloured to a greater or less 
extent by the presence of peroxide of iron. Although generally 
found in the New Red Sandstone, rock salt is by no means 
confined to this formation ; the deposits, for example, of 
Wieliczka, in Poland, and Volterra, in Tuscany, occurring in 
tertiary marls : from both these localities specimens are 
exhibited. 
The curious hopper-shaped crystals of salt here shown result 
from the aggregation of a number of small cubes formed on the 
surface of the brine during evaporation. 
The Greenland mineral called Cryolite or ice-stone is a double 
fluoride of aluminium and sodium, important as a source of 
aluminium (p. 56). Attention should be directed to the 
unusually fine crystals of the rare mineral called Glauber ite, a 
double sulphate of sodium and calcium, from Spain. The 
deliquescent nitrate known as Cubic nitre, or Chili Saltpetre 
has in recent years acquired great importance as a valuable 
fertilising agent. 
Case F. — Borax, Salts of Potassium, Magnesium, &a 
The collection in this Case commences wit h a series of specimens 
of Borax, a hydrated borate of sodium, of which some fine 
crystals are exhibited from Borax Lake, in California, and 
numerous small crystals from a lake in Tibet, whence large 
supplies were formerly brought into commerce under the name 
of lineal . Here also are shown many specimens illustrating the 
preparation of boracic acid from the soffioni or volcanic 
fumaroles of Tuscany. The hot vapours from these vents, 
contain only a small proportion of boracic acid, but are made to 
pass through water, by which the acid is absorbed, and this 
weak solution gradually becomes more highly charged, as it is 
transferred from one lagoon to another; when sufficiently 
impregnated, the solution is evaporated by means of the steam 
from the springs. The specimens exhibited are from the works 
of the late Count Larderel, whose name deserves record as the 
founder of this branch of industry in Tuscany. 
Among the salts of boracic acid may be noticed Hayesine ,_a 
borate of calcium, occurring in white reniform masses, scattered 
over the dry plains of Iquique in Chili, where it is called tiza. 
Boracite is a borate of magnesium, with chloride, remarkable 
for its electrical and optical properties. Colemanite, from 
California, and Panclermite from Asia Minor, are examples of 
H 2 
