Page:Transactions NZ Institute Volume 15.djvu/475
At Mokau the coal seams vary from 2 feet to 6 feet in thickness, and a trial of the coal against Waikato showed it to be one-fourth better, 1½ tons of the Mokau coal doing as much as 2 tons of the best Waikato (Hector, Geol. Rep. 1879–80, p. 21). The composition of these coals is—
| Fixed carbon | 52.10 |
| Hydro-carbon | 34.00 |
| Water | 11.20 |
| Ash | 2.70 |
| 100.00 |
At Whangarei two mines are at present at work—viz., Kamo mine, in which there are two seams 4 feet to 4½ feet and 8 feet to 12 feet thick respectively; and the Whau Whau mine, in which the seam is from 5 feet to 9 feet thick; besides which outcrops of coal occur at Whareora 3 feet to 3 feet 6 inches thick; and at Hikurangi, ten miles from Whangarei, there are numerous outcrops of coal from 2 feet to 6 feet thick.
The average composition of these coals from a number of analyses is: —
| Fixed carbon. |
Hydro- carbon. |
Water. | Ash. | ||||
| Kamo | 48.83 | 38.60 | 8.98 | 8.59 | |||
| Whau Whau | 47.50 | 41.45 | 7.59 | 3.46 | |||
| Whareora | 45.94 | 38.79 | 7.06 | 8.21 | |||
| Hikurangi | 43.41 | 45.67 | 6.16 | 4.76 |
making the average analysis of the coals from the Whangarei field—
| Fixed carbon | 46.42 |
| Hydro-carbon | 41.13 |
| Water | 7.45 |
| Ash | 5.00 |
| 100.00 |
Anhydrous Coals.
Glance Coals.—These, which are brown coals, altered variously in the vicinity of certain dykes and floes of dolerite, are only met with as workable seams in the Malvern Hills coalfield, where they occur as seams from 2 feet to 10 feet thick. They occur in all stages of change from brown coals to anthracites, and some of them might, with propriety, be classed under the subdivision of pitch coals, but since they all belong to a series, I have thought it better to group all that have undergone any degree of change under the present head, those in which the percentage of water is high being left with the brown coals. Some of these with a high percentage of water however, exhibit signs of change, the percentage of fixed carbon to hydro-carbon being large, as in the case of the seams at the Rakaia Gorge, already quoted. The following table of analyses shows how varied they are