Page:Transactions NZ Institute Volume 15.djvu/469

During the same year another sample of graphite was forwarded by Mr. Beere from the vicinity of Wellington, in which the percentage of carbon was 66.71; and Mr. P. C. Cheal also forwarded a very pure sample of graphite from Waiokura Creek, Waimate, Taranaki, the specimen having been found in the bed of a creek. In 1879 Mr. W. Docherty forwarded specimens of mica schist from Dusky Sound, in which scales of graphite were found; and in 1880 Mr. C. W. Tripp sent samples of graphite slate from the Orari Gorge, which contained 20.62 per cent. of carbon.

The only samples of this mineral which merit special description are those from Pakawau, Mount Potts, and Waiokura Creek

Graphite.—Pakawau. Compact, with lamellar and petaloidal structure; requires purification to render it of commercial value (Liversidge, Trans. N.Z. Inst., vol. x., p. 490); it is more or less schistose, and varies a good deal as regards purity.

Graphite.—Mt. Potts. Finely laminated; black and shining; powder soft, soiling the fingers; hardness about 1, but including small grains which are harder. Does not feel greasy to the touch. Appears to be an intermediate form between anthracite and graphite.

Graphite.—Waiokura Creek. A solid compact homogeneous form, separated in distinct laminæ about ¹⁄₁₆ inch thick with siliceous partings at places. Hardness a little over 1. Colour iron-black with black and shining streaks. Mark on paper corresponds with H. pencil. Has only been found as isolated boulders, the enclosing rock being unknown. It is an extremely valuable form of this mineral.

Coal.—This mineral is widely distributed throughout New Zealand, but samples from different localities vary greatly in their composition and value as fuel. In 1866 Dr. Hector (First General Coal Report) divided these into Hydrous and Anhydrous coals, or those which still contain a large percentage of water chemically combined with them, and those which we may assume to have been deprived of that water by a chemical change, which, in some cases, may have been induced by causes operating feebly throughout lengthened periods, or, in others, has been rapidly effected on more modern deposits of carbon, under circumstances which favoured a more energetic action. The large number of analyses which were subsequently made of the different classes of coals, together with a careful study of their prevailing characteristics, rendered it necessary to further subdivide them, and in 1872 Dr. Hector (Geological Reports, 1871–72, p. 172) proposed the following classification, which has proved so satisfactory that I cannot do better than adopt it in my present paper:—

I. Hydrous (coal containing 10 to 20 per cent. of permanent water.)

a. Lignite.—Shows distinct woody structure; laminated or shows that structure on desiccation; very absorbent of water.