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particulars in red will be found usefxil to prospectors, as the minerals to 

 which thej^ refer may often be recognised by their external form. A 

 crystallographic description is appended for the use of students. 



Streah. 



The colour of the powder of a mineral is one of the most useful aids to 

 its determination. This colour is best seen by drawing the mineral over a 

 piece of unglazed porcelain ; but it is quite sufficient to observe the colour 

 produced when the powder scratched or rubbed from the mineral is rubbed 

 on paper. 



A number of minerals are exhibited, the streak in each case accompanying 

 the mineral of which it is characteristic. It will be noticed that the colour 

 of the mineral is often A'ery different from that of its powder, a coloured 

 mineral frequently giving an almost colourless streak. Two or three 

 examples of particiilar importance-are as follows : — 



No matter how the various forms of hematite may differ from one another 

 in appearance, the streak remains the same — viz., blood-red. Cinnabar, 

 which is so commonly confounded with hematite, gives a scarlet streak. 

 Blende may be quite black, but its streak is never more than pale brown. 

 The pale streak of tinstone should prevent any possibility of mistaking 

 wolfram or limenite, which have red-brown and black streaks respectively 

 for it. 



Illustrations of characteristic streaks : — 

 Hematite : blood-red. 

 Cinnabar : scarlet. 

 Limonite : ydlow-hrown. 

 (Jrothite : brownish yellow. 

 Gold : yellow. 



Wolfram : dark reddish-brown. 

 •Graphite (plumbago) : black. 

 limenite : black to brown. 

 Molybdenite : greenish black. 

 Copper pyrites : greenish black. 

 Iron pyrites : greenish or broionish black. 

 Mispickel (arsenical pj^rites) : dark grey. 

 Antimonite : lead-grey. 

 Galena : same colour as the 7nineral. 

 Bismuth : silvery, with tinge of [.ink. 

 Blende : colourless to buff. 

 Chalybite : colourless to buff. 

 Tinstone : ivhite or pale-grey to brownish. 



