48 The N.Z. Journal of Science and Technology. [Jan. 
At the present time mica is sold in ten sizes, each divided into nine 
grades according to quality. The following table shows the range of 
prices :— 
Size. 
Area of Rectangular 
Plate obtainable. 
Price per Pound, according to 
Quality. 
Square Inches. 
s. 
d. 
s. 
d. 
No. 6 
1 
to 
3 
0 
6 
to 
1 
10| 
No. 5 
3 
to 
6 
1 
3 
to 
5 
0 
No. 4 
6 
to 
10 
2 
3 
to 
9 
0 
No. 3 
10 
to 
14 
3 
6 
to 
12 
0 
No. 2 
14 
to 
24 
5 
6 
to 
16 
0 
No. 1 
24 
to 
36 
7 
6 
to 
17 
6 
A1 
36 
to 
48 
9 
0 
to 
20 
0 
Special 
48 
to 
60 
10 
0 
to 
21 
6 
Extra s 
pecial 
60 
to 
72 
12 
0 
to 
23 
0 
Extra extra . . 
72 
and over 
15 
0 
to 
30 
0 
Consideration of these tables indicates that the lower grades of musco¬ 
vite mica have more than doubled in price, whilst the higher grades have 
apparently not quite doubled in value. It is not certain, however, that the 
two tables can be exactly compared. 
Scrap mica a few months ago was worth in the London market 3s. 
to 3s. 6d. per hundredweight, which is not a great advance on pre-war 
prices. 
Phlogopite mica is in demand, but does not bring as high prices as 
muscovite mica. 
Preparation of Mica for Market. 
As it comes from the mine the mica is in blocks of all sizes and shapes. 
The outside portions are often opaque, brittle, and worthless, and these, 
of course, have to be discarded. Material that is obviously valueless owing 
to cross-grain, &c., is also thrown aside. The merchantable mica is split 
into sheets or thin slabs from ^ in. to J in. thick. These are roughly sorted 
according to size, and carefully trimmed so that all rough edges, cracks, 
and inclusions are cut away, almost regardless of what shape the pieces 
may assume, though it is desirable that the trimmed material should not 
have more than five or six sides. Each piece in the larger sizes is care¬ 
fully cleaned as much as possible. The sheets are finally regraded accord¬ 
ing to size, and the sizes are graded according to quality. The grades at 
present in vogue are—Clear, Government standard ; part stained, Govern¬ 
ment standard; second quality, clear; second quality, part stained; fair, 
stained ; ordinary, rust- and clay-stained ; densely stained ; soft white ; 
black-spotted. 
Buyers of Mica. 
The following British firms are buyers of mica :— 
Attwater and Sons, Hopwood Street, Preston. 
Baker and Smith, 19 St. Dunstan’s Hill, London E.C. 3 
