MINERALOGY OF BLACK LAKE AREA. 
45 
secondary actinolitic material, in the form of very pale green to colour- 
less shreds or fibres. 
Short fibres, often radially grouped, of pale green actinolite, are 
associated with the colerainite in the specimens from the old Standard 
mine described on page 66. 
GARNET. 
From a crystallographic standpoint the garnets are amongst the 
most interesting minerals occurring in this area. Crystals exhibiting 
two quite exceptional features have been noted ; these are amber-coloured 
grossularite, fairly rich in forms which present the very unusual cube 
faces, and pale rose crystals, which occur as simple six-faced octahedra. 
Still another point of interest is the occurrence of grossularite in colour- 
less crystals. 
Garnets were found at most of the localities visited, and are of 
two varieties, grossularite (calcium-aluminum garnet), and andradite 
(calcium-iron garnet). Only the colourless grossularite occurring at 
the Southwark pit has been completely analysed; beyond this, the 
classification of the crystals as grossularite and andradite is here 
based on their behaviour with hydrochloric acid and before the blow- 
pipe. Crystals which are partially soluble in concentrated hydro- 
chloric acid and yield gelatinous silica on evaporation, and which also 
fuse to a globule that is strongly magnetic, have been classed as andradite; 
those which do not give these reactions, as grossularite. Subdivided in 
this way it has been found that the colourless, rose, and certain greenish- 
yellow crystals are referable to grossularite, while the andradite is always 
olive to apple-green in colour; the former crystals moreover are usually 
transparent and dodecahedral in habit, while the andradite is inclined 
to be opaque and invariably exhibits the trapezohedron as the dominant 
form. 
The crystals are all rather small, none having been observed with a 
diameter greater than 1 cm. A description of the principal occurrences 
follows: 
Occurrences. 
Union Pit. Cavities in a fairly compact, rose-coloured, grossular- 
garnet rock are lined with well crystallized garnet of the same or paler 
colour, accompanied in many places by a little aragonite and brown 
diopside. 
Many of these crystals are simple dodecahedra, while on others the 
trapezohedron n( 211) is also present as narrow truncating faces. The 
dodecahedron faces are frequently striated parallel to the shorter diagonal, 
and, in the case of some of the crystals, each dodecahedron face is seen 
to be in reality double, being made up of two very slightly inclined faces, 
