Meddelelser Om Gronland Volume 24 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1901 edition. Excerpt: ...it follows that, if the two acids hud been separately determined, the ratios for them would have been less than those now found. Also the ratio for i?2 0 and F is a little too high. This may possibly be due to a somewhat too high result of the water determination. Chalcolamprite thus consists of equivalent amounts of J.'" the substances RNbtOuFt and RSiO3. Common pyrochlore consists of the same niobium compound and, as it seems, varying amounts of RTiO3, where Ti may be replaced by Th, Zr etc. On account of varying results of the analyses it has not as yet been possible to establish a generally acceptable formula for pyrochlore. Rammelsberg') has come to the result that pyrochlore consists of isomorphous mixtures of NaF, RNb20U) ASAT6,0, and ETi03 or RTiO2, etc. Apart from the improbability of such heterogeneous combinations replacing one another isomorphously, this requires that Na and F should be present in equivalent quantities, which is not always the case in pyrochlore nor ever in chalcolamprite. As a result of his synthetic investigations Holmqvist8) finds the formula NaCaNb2OiF for the pyrochlore-minerals. However, this formula has no place for the combinations BTiOs, ThOa, etc. which are present in all natural pyrochlores. ') Monatsber. Berliner Akad. 1871, p. 203. ) Inaugural Diss. Bull, of Geol. Inst. Upsala, 1896. Vol. Ill, p. 1. Chalcolamprite has been found only at the locality No. 7 on Narsarsuk. Only a scanty supply of the mineral could be collected. As already mentioned, the chalcolamprite crystals occur partly implanted on larger aegirine individuals, partly attached to a network of thin needles of the same mineral. Such fine aegirine needles often penetrate the chalcolamprite crystals; they are, ...