19 
Insoluble in acids; slightly fusible by itself in small 
splinters; with borax it gives a green glass, in which 
oxide of iron is indicated ; with salt of phosphorus silica is 
separated. It is frequently found with cyanite in the 
micaceous schist of the Gotthardt, and at Sterzing in the 
Tyrol, in the Pyrenees, North America, New England, 
Chesterfield in Missouri, near New York, etc. Particularly 
fine twin crystals occur at Oporto and St. Jago di Com- 
postella in Spain, also in Bretagne. 
Figs. 6 and 7.— Andalusite. 
Right rhombic prism, with slight displacement of the 
lateral planes at angles of 91° 33 ; and 88° 27 y ; occasionally 
with truncation of the acute angles, as Fig. 6. Frequently 
in twins or quadruplets (Fig. 7), with clay-slate interven¬ 
ing, so that in a transverse section very fine cruciform 
figures are brought into view. Sometimes these crystals 
are hollow, and for this reason are named hollow-spar or 
chiastolite. 
The colour is pearl-grey, reddish, or violet, the lustre 
slight, and it does not take on a particularly good polish. 
The fracture is unevenly splintered. Generally opaque or 
slightly translucent. Hardness = 7*5 ; specific gravity = 
31. 
Burns with a white flame before the blowpipe without 
being melted ; insoluble in acids. 
The chemical constitution is as follows: silicate of 
alumina (Al 3 Si 2 ), sometimes with slight traces of chalk, 
magnesia, and oxide of iron. 
It is found, especially in the primary rocks, at Lisens 
in the Tyrol, Penig in Saxony, Iglau in Moravia, Litch¬ 
field and Washington in Connecticut, Leiperville in Penn¬ 
sylvania, Killiney Bay in Ireland. The hollow-spar occurs 
at St. Jago di Compostella in Spain, at Bayreuth in the 
Fichtel mountains, and in Cumberland. 
Figs. 8-11.— Tourmaline, Electric or Rhombohedral 
Schorl. 
The primary form is an obtuse rhombic hexagon, as 
seen in Fig. 9. They usually occur, however, as six, nine, 
and twelve-sided prisms, having their origin in the trunca¬ 
tion of the basal edges and angles, as is seen, for example, 
in Figs. 8, 9, and 11. Sometimes three crystals are 
united twin-wise, like Fig. 10; truncation of the vertical 
angles (Fig. 10) and of the vertical edges (Fig. 11) also 
occurs. The lustre is lively vitreous ; the lateral planes 
are mostly striated vertically ; there are very long acicular 
crystals, and others very thick and almost as large as the 
hand. The colour varies much; there is black, green, 
blue, red, and even white tourmaline ; transparent varieties 
are called noble or precious tourmaline; the opaque com¬ 
mon tourmaline ; those which are colourless are called 
achroite or apyrite , and the blue ones indicolite. 
The hardness slightly exceeds that of the rock-crystal 
(7—7 - 5) ; the specific gravity is = 3 , Q—3’5. The fracture 
is uneven or conchoidal. 
The elements are silicate of alumina, with borate and 
carbonate of magnesia, lithium, sodium, potass or protoxide 
of iron. 
When heated, the long crystals especially acquire polar 
electricity, so that small bodies are attracted by one 
end and repelled by the other. For this reason it is 
sometimes called electrical schorl. Before the blowpipe 
small splinters melt into a brown or black slag; with 
borax the powder is fused into a clear glass, from which 
silica is extracted by salt of phosphorus. 
It occurs principally in the primary rocks; granite con¬ 
taining tin, chlorite and micaceous schist are especially 
rich in specimens, as for example in the Tyrol and Nor¬ 
way. The green tourmaline is found in the dolomite near 
Campo Longo. Fine red and blue specimens occur in 
Brazil and Siberia. The finest and largest black tourma¬ 
lines are from Greenland, and Modum in Norway; short 
black forms stamped with rhombohedrons, the so-called 
aphricite , are found imbedded in quartz at Bamle in South 
Norway. 
Finely-coloured transparent tourmaline, when polished, 
are used as stones for ornaments; the red, blue, and green 
colours are most esteemed. Small stones of one carat weight 
cost from 6s. to 8s.; dark green of 6 yy/ length by 4 ;y ' in 
breadth are worth £2 : 10s. to £3 :10s. It may easily be 
distinguished from coloured glass by its hardness and 
electrical properties, while, on the other hand, it may be 
distinguished from the ruby, sapphire, and emerald by its 
lower degree of hardness and by the difference in colour. 
Figs. 12 and 13.— Pelioma, Diohroite, Cordierite, 
Lynx-Sapphire, Water-Sapphire, Iolite. 
Pelioma is generally found in six-sided prisms, with 
plane terminal faces, truncated in the basal edges, as seen 
in Fig. 12, sometimes also with further truncations, espe¬ 
cially of the lateral edges; also of the basal angles, or in 
rounded granules and compact masses; the primary form, 
nevertheless, is a right rhombic prism of 120° and 60°, in 
the direction of which it may be split. The split surfaces 
are tolerably even, splintery and crystalline; this circum¬ 
stance serves to distinguish it from quartz, which, however, 
possesses the resinous-like lustre; it has also the same, or 
even a less marked hardness (=7—7'5). Its specific gra¬ 
vity is = 2*5—2'6. 
When seen by transmitted light, the colour is bluish- 
brown or greyish-yellow, according as it is held in a per¬ 
pendicular or horizontal direction; when cut, therefore, it 
usually exhibits a double play of colours, and for this rea¬ 
son it has been called lynx-sapphire ; transparent fragments 
present double refraction of rays. 
The composition is silicate of alumina and silicate of 
magnesia, and protoxide of iron. 
In the blowpipe flame it melts when reduced to small 
fragments, and is readily distinguished from quartz. Pure 
transparent crystals are found principally in Ceylon and 
Brazil, and if they are of a fine blue, they are cut as 
stones for ornaments, especially for rings, under the name 
of water-sapphire. One of the size of Fig. 13 is valued 
at from 15s. to £1. There are also good crystals at 
Bodenmais in Bavaria, in Finland, Siberia, and Greenland; 
it occurs in a compact form at Twedestrand in Norway, 
and in North America. In Ceylon and Brazil it occurs 
in boulders. 
