THE MINEEALS OF TASMANIA. 



mineral is remarkably gum-like. The composition is quite 

 unusual, but there is little doubt about the identification. 

 Analysis by Mr. Watson, la€e of the Magnet Silver- 

 mining Company : — 



Very characteristic samples of this amorphous mineral 

 occur in reniform masses of a pale colour, almost trans- 

 lucent, and with a waxy lustre, at the Upper Forth. 



8. Alunogen (Sulphate of Aluminium). 



Often abundant as an efflorescent powdery to fibrous 

 incrustation in caverns and under shelving ledges, occur- 

 ring in connection with saliferous rocks. It occurs near 

 Bridgewater ; Brown's River-road ; near St. Marys ; Mer- 

 sey River, about 4 miles from Chudleigh, known locally 

 as the Alum Cliff ; Blue Tier, near Beaconsfield ; and in 

 other localities. 



9. Amphibole Group. 



This is an important group of rock-forming minerals 

 which are almost exclusively confined to the Plutonic 

 series ; the exception being those sometimes found in true 

 lava, i.e., basalt and trachyte. They are chemically allied 

 to the pyroxenes, but differ in the angular measurement, 

 their cleavage, and their larger and more blade-like habit. 

 The amphiboles may be termed the long, while the 

 pyroxenes are the short, examples of a similar series of rock 

 constituents, which closely approximate both in chemical 

 composition and physical characters. The group, although 

 so closely parallel to the pyroxenes, is less numerous in 

 species, and so far as described the members also show 

 less variety of form. They nearly all crystallise in the 

 monoclinic system, the exceptions being anthophyllite, 

 which belongs to the orthorhombic, and cossyrite to the 

 triclinic, system. The various members of the group occur 

 generally confusedly aggregated in habit, but may be 

 fibrous or columnar in growth. In lustre they are vitreous 

 to pearly on cleavage faces, opaque to translucent, and 



