76 NOTES ON TASMANJAN MINERALS. 



cavities in somewhat soft iron-manganese gossan. 

 The coated surfaces are often met with of reason- 

 able size, and have been obtained covering several 

 square inches of the gossan, more especially where 

 vughs and fractures occur. More rarely bunches 

 of galena are wholly or partially covered by the 

 substance. It is often in crypto-crystalline 

 incrustations, occasionally pulverulent, and more 

 rarely in bunches of hexagonal crystals of almost 

 microscopic dimensions. The largest crystals so 

 far observed were but three millimeters in length, 

 but the outline was sharp and very distinct. The 

 crystals are of adamantine lustre, and a 

 remarkably bright red to crimson colour. Minute 

 acicular patches of crystals are common, and 

 under the lens are perfectly distinct, and thus 

 afford very fine microscopic objects of consider- 

 able attractiveness. The bright crimson colour 

 of the general mass is very characteristic, and by 

 this feature it is noticeable by the most casual 

 observer, even when not directly interested in 

 mineralogy. It sometimes occurs in aggregates 

 of extremely minute needles, much like velvet, 

 of a distinct and bright yellow to orange colour, 

 and in this form it also occasionally coats some- 

 what large surfaces. Chromiferous cerussite and 

 more rarely crocoisite and mimetite are inti- 

 mately associated with it. Although so notice- 

 able, the coating of the substance is usually of 

 such extreme thinness that it was only with the 

 groatast difficulty and by using the utmost care 

 that enough was secured to make a complete 

 analysis. This was undertaken by Mr. J. D. 

 Millen, A.S.T.C, M.S.C.I., Lond., metallurgical 

 chemist to the Mt. Bischoff T. M. Co. The 

 following is the result: — 



99-159 



