BY W. F. PETTERD, C.M.Z.S. 149 



admixture in the lode gangue of the silver-lead mines ; and 

 on the West Coast crystals coloured red with iron oxide 

 have been obtained. At Beaconsfield a honeycombed form 

 occurs; this apparently has resulted from the decomposi- 

 tion of pyrites. Masses of a similar character have been 

 found at the Pieman River and other places. 



At the Vale of Belvoir, quartz occurs pseudomorphous 

 after tremolite, and silicified wood^ which is of similar 

 origin, is abundant in many places. At Ben Lomond, 

 in the workings of one of the tin mines, quartz has been 

 found pseudomorphous after felspar ; the specimens have 

 a peculiar mottled appearance of various shades of brown. 



A peculiar variety known as " hacked quartz '' occurs at 

 several of the East Coast alluvial tin workings and at the 

 Lisle goldfields. Some specimens from the lastmentioned 

 locality are remarkably fine and fresh, as well as being of 

 unusually large size — at times quite 2 feet in length. The 

 origin of this variety has caused no little speculation. Its 

 original home was probably formed by the infiling of vughs 

 in the granite rock. The peculiar hacked impressions on 

 most of the faces of the irregular mass are the imprints on 

 felspar or other crystals which originally lined the cavity. 

 It would appear that silica in solution percolated through 

 the granite into the cavity, and in hardening, retained 

 the image of its form and lining, thus becoming the verit- 

 able casts which are now found in the alluvium. 



At the Hercules Mine, Mt. Read, many of the small 

 quartz crystals are both " left-handed " and also " right- 

 handed," and in some cases, in addition to the W and 

 Y trapezoids, show the rhombic face &. The last has 

 also been detected in some of the crystals from the vicinity 

 of Bell Mount, Middlesex. At the North Lyell Mine 

 many small quartz crystals occur, which are flattened in 

 the plane containing the principal axes, and mackled with 

 another crystal on 521 intersecting in a zig-zag line. These 

 twins are known from the Dauphine, and also from Japan. 



On the sand hillocks skirting portion of the coastline of 

 Flinders Island, Bass Strait's, novel forms of siliceous con- 

 cretion have been collected. They are known as fulgurites 

 or vitrified sand, produced by the action of lightning on 

 the sand dunes. They are circular, thin, about 2J inches 

 in diameter, with a concentric structure, and more rough- 

 ened on what is apparently the upper surface than 

 the lower. 



" On the Linda track, between the Rivers Collingwood 

 and Franklin, a remarkable pisolitic variety occurs as loose 



