16 



THE MINERALS OF TASMANIA. 



31. Atacamite (Oiy chloride of Copper). 



This beautiful green ore of copper is occasionally met 

 with in radiating acicular bunches in the vughs of ferro- 

 manganese gossan ore capping the lode on the property of 

 the Comet Silver-mining Company, Dundas ; in small 

 quantity in mixed oxidised ore, Silver Queen, Zeehan ; and 

 in vughs, Gad's Hill Range, Upper Mersey River. 



32. AuGiTE f^A Dark-coloured Variety of Pyroxene). 



The crystals of this mineral are usually, if not always, 

 stouter proportionately than those of its ally, hornblende, 

 and they are but rarely much elongated. In the basic rocks 

 they are fairly developed. 



Localities: St. Paul's Plains (Pro. Royal Soc. Tas., 

 1854) — in basalt, the crystals are often nearly half an 

 inch in length : Paddy's Sugarloaf , Emu River ; Hamp- 

 shire Hills, near the Emu River ; near Mt. Horror, in an 

 intensely black basalt, on the weathered portions of which 

 the crystals stand out from the surface of the rock ; they 

 are often very clearly defined. 



" This mineral occurs abundantly in well-formed crystals 

 up to a quarter of an inch in size in the basalt of the point 

 of eruption near Hampshire Hills. (The Mt. Bischoff rail- 

 way-train passes close to the right of this basalt hill going 

 up.) Crystals can also be washed from the basaltic detri- 

 tus on the slope of the hill. They mostly form twins 

 according to the common law — twinning and composition 

 plane the orthopinacoid." (Ulrich.) 



The embedded crystals in the nephelinite of the Shannon 

 Tier are of a shining black colour, and often of remarkably 

 large dimensions, sometimes one inch and a half long. This 

 monoclinic sub-species of pyroxene is an essential constitu- 

 ent in many volcanic rocks, such as basalts, as well as 

 dolerite and other basic igneous rocks. It is almost always 

 black or very dark in colour, and opaque. It commonly 

 occurs crystallised, but may be in angular fragments, or 

 even rounded grains, and is in some instances, such as in 

 dolerite, of an ophitic character, clearly enwrapping the 

 feldspathic ingredient. The crystals are generally small 

 and imbedded, but on the exposed surface of the rock 

 they are often prominent, and not rarely weathered out, 

 as is the case with the occurrence at the Hellyer River. 



