AUSTRALIAN MUSEUM SCIENTIFIC PUBLICATIONS Anderson, C., 1905. Mineralogical notes. No. II. Topaz, barite, anglesite, cerussite, and zircon. Records of the Australian Museum 6(2): 83–97, plates xviii–xx. [15 September 1905]. doi:10.3853/j.0067-1975.6.1905.991 ISSN 0067-1975 Published by the Australian Museum, Sydney nature culture discover Australian Museum science is freely accessible online at http://publications.australianmuseum.net.au 6 College Street, Sydney NSW 2010, Australia MINERALOGICAL NO'l'ES: No. II.-'l'OPAZ, BARITE, ANGLESITE, OERUSSITE, AND ZIROON. By O. ANDERSON, M.A., B.Sc., Mineralogist. (Plates xviii.-xx.) TOPAZ. EMMAVILLE, NEw SOU'l'H WALES. Since a description and figures of topaz crystals from Emma­ ville was published, 1 Mr. D. A. Porter has presented to the Trustees the specimen represented in PI. xviii., Fig. l. It is a typical and finely developed example of the crystalline habit of topaz from this locality, and, as it is somewhat larger than the best crystals hitherto examined, it is possible to represent the faces in approximately their actual relative proportions. As usual there is a comparatively rich prism zone, with the form m (llO) greatly predominating. Each of the prisms has four faces, present, but the pinacoidb (010) has only one. The three domes have each the full number of faces. Of the pyramids 0 (221) and x (243) have. but three faces, while u (llI) and i (223) have four. The faces are with few exceptions smooth and brilliant and give excellent reflections. The crystal measures 9t mm. x 5t mm. x 4 mm. The mean co-ordinate angles obtained areas follows :- 1 Anderson-Rec. Austr. Mus" v., 1904, pp. 296·299, pI. xxxix., figs. 1-3 84 RECORDS OF THE AUSTRALIAN MUSEUM. Measured. CaIculated. Error. Forms. -------- -,--- cp p cp p cp p ----------I -- 0 , 0 , 0 , 0 , , , c 001 - --- -"- - -- -- b 010 0 15 90 5 0 0 90 0 15 5 m 110 6:2 4 90 2 62 8 90 0 4 2 JYI 230 51 34 90 1 51 35 90 0 1 1 l 120 43 24 90 3 43 25 90 0 1 3 7r 250 37 8 90 0 37 7 90 0 1 0 9 130 32 16 90 0 32 14 90 0 2 0 d 201 89 59 60 59 90 0 61 0 1 1 f 021 0 1 43 37 0 0 43 39 1 2 '!J 041 0 0 62 19 0 0 62 20 0 1 0 221 62 8 63 52 62 8 63 54 0 2 u III 62 8 45 36 62 8 45 35 0 1 i 223 62 6 34 15 62 8 34 14 2 1 x :243 43 27 41 14 43 25 41 12 2 2 In this as in succeeding tables the calculated angles are those given by Goldschmidt in his Krystallographische Winkeltabellen. Since a considerable number of angular measurements of topaz crystals from Emmaville are now available, it may be of interest to calculate the corresponding axial ratios, especially as Penfield and Minor2 have shown that the ratios vary with the isomorphous replacement of fluorine by hydroxyl. For this purpose the angles were carefully revised, the best measurements selected, and means taken. The forms chosen from measurements on six crystals and the mean angles obtained are given in the table below; as it was judged that the prism m and the pyramid u yield the most reliable data, the corresponding values for a and c are counted twice in finding the mean ratios. 2 Penfield and Min0r-Amer. J0urn. Sci., xlvii., 1894, p. 387. MINERALOGICAL NCrrES-ANDER30N. 85 1 Furm.\ 1> p a c I I 0 , 0 , 1- " " m 110 62 7 38'5 '5288615 l 120 43 25 5 '5284015 g 130 3:2 14 24 '5285428 u III 62 7 38 45 34 40 '5288646 '4769763 j 021 43 39 '4770300 Y 041 62 19 30 '4767101 Mean ... ... 0'5287328 0'4769232 The calculated values of et and c agree fairly closely with Koksharov's ratios a: b: c = 0'528542 : 1 : 0'476976, determined on Russian topaz and usually taken as the standard. PI. xix., fig. 1 is a stereographic projection showing the distribu­ tion of all faces that have been identified on Emmaville topaz. OBAN, NEW SOUTH WALES. Mr. D. A. Porter recently presented to the Trustees a fine large crystal of topaz from Oban. It measures 4 cm. x 4 cm. x 3 cm., and shows four forms not recognised on crystals from this locality hitherto examined, namely c (001), d (201), h (203), and X (043). It is shown in its natural development in PI. xviii., fig. 2. The specimen is somewhat worn and the faces non­ reflecting, but approximate measurements obtained with the contact goniometer leave no doubt as to the correctness of the determinations. There is but one face of X present, but all the others have the full number. One of the .I (021) faces shows a distinct natural etching-figure. It takes the form of a raised semicircular area with its convexity directed towards the apex of the crystal, the base of the semicircle being parallel to the inter- 8ection of .I and c. MOUNT CAMERON, TASMANIA. Through the kindness of Mr. W. F. Petterd, a well-known authority on the minerals of Tasmania, I have been en3,bled to 86 RECORDS OF THE AUSTRALIAN MUSEUM. measure some fine specimens of crystallised Tasmanian minerals, including topaz from Mt. CamerOll, Flinders Island, and Bell Mount. At Mt. Cameron topaz is abundant in the stanniferous drift, but has not been found in situ. It is usually much worn, but some crystals well suited for crystallographic determination were sent to me by Mr. Petterd. Two crystals were determined on the goniometer, one a crystal measuring 12 mm. x 13 mm. x 12 mm. and of a greenish colour shown in PI. xviii., fig. 3. It is fairly rich in prism faces, having m (110), M (230), l ( 120), and g (130) present; l predominates, but all are well marked faces and give fairly good images. The terminal faces are rather dull; only one face of 0 (221) is present. The co-ordinate angles obtained are given below. Measured. 'calculated. \ Error. Forms. ------.------ --~~.---~-- :'---.,--- _______ __ o_<P__ , -I--o-P-,-I-o-<P-,-I--o-P--I _1 __<P_ -Il-o-P-, 1 c 001 m 110 62 5 89 56 62 8 90 0 3 4 J.1£ 230 51 28 89 53 51 34 90 0 6 7 l 120 43 17 89 55 43 25 90 0 8 5 g 130 32 19 89 55 32 14 90 0 5 5 f 021 6 43 35 o 0 43 39 6 4 y 041 8 62 l,l o 0 62 20 8 7 o 221 61 57 62 53 62 8 63 54 11 11 U III 62 7 45 29 62 8 45 35 1 6 t 223 62 7 34 13 62 8 34 14 1 1 From another lot of small clear, colourless, crystals one was selected and its faces determined (PI. xviii., fig. 4). It measures 7 mm. X 5 mm. X 5 mm., and in general habit resembles the last, but has fewer prism faces and has the rather rare pyramid x (243) fairly well developed but dull. The prism faces are striated and give only fair signals. Appended are the mean co-ordinate angles found. MINERALOGICAL NlffES--ANDERSON. 87 Measured. Calcul"tec.. Error. For,m I I P I P CPI I -----.-----------[--- c 001 ~ ~ ~ ~ ~ ~ I ~ ~ ~ ~ m 110 61 58 89 58 62 8 I 90 0 10 2 l 120 43 7 89 58 43 25 90 0 18 2 f 021 1 43 37 0 0 43 39 1 2 Y 041 7 62 13 0 0 62 20 7 7 u III 61 53 45 24 62 8 45 35 15 11 i 223 61 46 33 58 62 8 34 14 22 16 x 243 42 26 41 6 43 25 41 12 59 6 FLINDERS ISLAND, TASMANIA. Topaz from Flinders Island was first mentioned, I believe, by the late Rev. J. J. Bleasdale, D.D., who )Vrote: "This may be said of those [i.e., topaz crystals] from Flinders Island that they possess very great fire and beauty when cut, and are nearly all of a pale yellowish shade in the rough.''' The best account of the occurrence is that of the late C. Gould, Government Geologist of Tasmania, who observed it whilst making a geological re­ connaissance of the islands in Bass Strait. 4 The following paragraph gives an abstract of his observations. It occurs in crystals and pebbles in great variety of form, colour and size, associated with zircon, tourmaline, cassiterite, etc. It is derived from the granite and may occasionally be obtained as fine crystals in situ along with crystallised quartz and felspar. It is abundant on the north-east side of Killicrankie Bay in a creek descending from the ranges and upon the beach; it also occurs in other parts of Flinders Island. 'l'he topaz has evidently been formed in veins of pegmatite which traverse the granite and vary from one to several feet in diameter. The colour varies from pure limpid to various shades of blue, pale pink, yellow, etc. Crystals are found up to several inches in diameter. 3 Bleasdale-Trans. Roy. Soc. V\(~t .• vii., 1860, p. 70. 4 Gould-Proc. Roy, Soc. Tas., 1871 (1872). pp. 60-61. 88 kECOlWS m' '!'HE AUSTRAl,IAN MUSEUM, A fine crystal (PI.