118 
THE PRINCIPAL FLOOR. 
in Western Cornwall. The mineral is remarkably unctuous to 
the touch, and is hence popularly termed soapstone : advantage 
is taken of this property in using powdered steatite for causing 
new gloves and boots to slip on readily; the variety employed 
for this purpose being generally known as French chalk. Soap- 
stone resists the action of heat and has been employed for 
gas burners and for lining stoves ; at one time it was used in 
the manufacture of porcelain at the Worcester Works. When 
lamellar it is generally known as Talc, a name frequently applied 
improperly to mica ; the two are however easily distinguished, 
the talc being flexible but not elastic, whilst the mica enjoys 
great elasticity. 
Case W. — Serpentine, &c. 
Enough has already been said of serpentine as a rock, when 
describing the fine objects in the Hall (p. 28). Other examples 
of this ornamental stone are in this Case, where also will be found 
specimens of noble or precious serpentine, a variety of oil-green 
colour, slightly translucent ; of chrysotile and picrolite, the one a 
iibrous and the other a columnar variety ; of marmolite and 
antigorite, the former a foliated, and the latter a lamellar form 
of serpentine. 
It is the mineralogical student rather than the general visitor 
who will be interested in most of the other minerals in this 
case. The Lemnian earth, formerly valued in medicine, was 
esteemed sacred by the ancient Greeks, being mixed with goats’ 
blood, and made into cakes, which were then stamped by 
the priests, whence it was called sealed or sacred earth. From 
the use of the Agalmatolite by the Chinese for carving figures 
it has received the names of figure stone and pagodite. Several 
distinct substances, however, are used for these Chinese carvings. 
The white powder labelled Kaolinite represents in a state of 
purity the hydrous silicate of aluminium which in less pure forms 
constitutes part of our kaolin or China-clay (see p. 120). 
Case X. — Zeolites. 
The zeolitic minerals occupying this and the following Case 
are related by several characters in common. They may be 
regarded as essentially hydrous silicates of alumina with an 
alkali or an alkaline earth ; and are usually found in the cavities 
of amygdaloidal trap-rocks, some, however, occurring also in 
metalliferous veins. Beautiful in their crystalline forms, and 
interesting in their chemical composition and mode of occur- 
rence, the zeolites are highly attractive to the mineralogist, but 
they receive no practical applications. The principal species 
represented in this Case are Frehnite, a hydrous silicate of 
aluminium and calcium, of which some examples are exhibited 
from the igneous rocks of the Dumbarton Hills ; analcime, a 
hydrous silicate of aluminium and sodium, often containing also 
potassium and calcium ; and apophyllite , a mineral differing from 
