THE MINERALS OP NEW SOUTH WALES. 203 



Zircon, Hyacinth, Jargoon. 



Chem. comp. Zirconium silicate. Pyramidal system. 



The transparent red varities are known as hyacinths, the smoky 

 jargoon ; while the grey, brown, etc., are known as zircons. 



This mineral is found in granite on the Mitta Mitta, and on the 

 Moama River, some 4 miles west of Jillamalong Hill. 



Zircons are very common in the auriferous river sands and 

 drifts, as at Uralla, Bingera, Two-mile Flat, the Cudgegong, Mac- 

 quarie, Abererombie, Shoalhaven, and other rivers. 



They are of course usually more or less rolled, but occasionally 

 the crystalline form is well preserved ; they vary much in colour, 

 from more or less colourless and transparent through pale-red to 

 crimson, brown, and opaque ; they are also found of a clear trans- 

 parent green, but these are rarer than the others. 



Topaz. 



Chem. comp. : Aluminium, silica and fluorine. Rhombic system. 

 Occasionally met with in well-formed columnar crystals capped 

 with planes of numerous pyramids. The best-formed crystals 

 are usually perfectly clear, colourless, and transparent. Some 

 very large crystals have been met with; a portion of a large bluish 

 green-coloured crystal found at Mudgee, and now in the Melbourne 

 Technological Museum, weighs several pounds; and others weighing 

 several ounces are by no means rare ; they are sometimes 2 to 3 

 inches long and broad in proportion, especially those from Uralla. 



The pale bluish-green tint is the most common colour, some- 

 times they are slightly yellow. 



It is comparatively abundant all over the granite region of New 

 England; it occurs associated with tinstone in veins traversing the 

 eurite and greisen granites near Elsmore and other parts; some of 

 the small crystals found with the tin ore are beautifully developed. 



Found also at Bingera, Two-mile Flat, Bathurst ; Bell River, 

 also Macquarie, Abererombie, Shoalhaven, and Lachlan Rivers. 



Spinelle. — Spinel Ruby. 



Chem. comp. : Magnesium aluminate. Cubical system. Small 

 well-formed octahedra are by no means rare ; the colour varies from 

 pale brown, red, deep crimson, green, to black (pleonaste). 



It is found in most river deposits containing gold, as in the 

 sands of the Severn and its tributaries, at Uralla, Bingera, Two- 

 mile Flat, Bathurst, Macquarie, and Cudgegong Rivers. 



Pleonaste. — Fairly well-formed large crystals of pleonaste with 

 well-marked conchoid al fracture are found in the Lachlan River. 

 One fairly well-formed octohedron, from the Muntabilli River, 

 Monaro district, was remarkable for its channelled faces. 



