MISERALO GIC A L CHE 111 S T R Y . M in e r a1 o g i c a 1 C h e m i s t ry. 109 Native Platinum from Canada. By G. C. HOFFMAN (Jahrb. j : Xin., 1888, ii, Ref., 386, from Geol. Szcrv. Can. Rep., 2, 5).-Native platinum has been found with gold in several rivers in British Columbia. From the bed of Granite Creek, a tributary of t h e Sixnilkameen river, grains were obtained varying in diameter froin 1 to 4 inm., and weighing altogether 18.266 grams. The material was separated into a magnetic (1) and a non-magnetic portion (H), the compositions of which were as follows :- Pt. Pd. Rh. Ir. Cu. Fe. OsIr. Chromite. Total. 1. 78-43 0.09 1.70 1.04 3-89 9.78 3-77 1-27 99.97 11. 68-19 0.26 3-10 1.21 3.09 7.87 14-62 1.95 100.29 The sp. gr. of the magnetic portlion was 16.095, and that of the The Pyroxenites of Morbihan.By C. BARROIS (Jahrb. f. Nin., 1888, ii, Ref., 413-414, from Ann. SOC. ge'ol. du Nod, 15, 69-96). -The pyroxenites of Morbihan form beds 0.1 to 2 metres in thick- ness in gneiss and mica-schists of Archean age. The main con- stituent of these rocks is a pale green augite of the fol1owi:ig composition :- non-magnetic portion 17.01. B. H. B. SiO3 CaO. MgO. Fe20,. Al,O,. Na,O. K,O. Total. 51.5 24.3 11.9 8.3 5.0 1.1 trace 102.3 The augite is accompanied by zircon, titanite, and apatite in small quantities, by garnet and idocrase in varying amounts, and by quartz grains associated with felspar. Irregular grains of orthoclase only occur in certain beds, and microcline is also of exceptional occurrence. A fibrous actinolite is, ho wever, present inlarge quantities, in many cases replacing the augite, so that rocks resembling nephrite are produced.Titaniferous iron ore and ferric hydroxide are also present. By t h e variety of the character and relative proportions of the constituents, numerous distinct types are distinguished, which may occur in the same bed. The author regards these pyroxenites as metamorphic limestones. B. H. B. Riebeckite, and the New Formation of Albite in Granitic Orthoclase. By A. SAUER (Chem. Centr., 1888, 1128, from Zeit. deut. geol. Gess., 40, 138--152).-A new member of the hornblende- granite group has been found by the author in Socotra. This horii- blende, named riebeclzite, has the same composition as arfvedsonite, arid is the analogue of agirin of the augite series.From the analysis (No. 1 below) the formula 5FeSi0,,4Na&3i0,,5Fe,Si3O9 has been calculated.110 ABSTRACTS OF CHEMICAL PAPERS. The Socotra granite is much disintegrated, and the author was thus enabled to examine more completely certain interchanges in the granitic orthoclases. The microscopical examination showed an opalescence from the edge towards the centre of the crystals, occa- sioned by the formation of albite, the crystals having been originally perfectly clenr and without inclosures. The following are tlte analyses of riebeckite (1) and the secondary albite (2) :- SiOP Al,O,. Fe,03. FeO. MgO. MnO. CaO. Ntx20. K,O. (1.) 50.01 - 28.30 9-87 0.34 0.63 1-32 8-79 0.72 - - 6.86 5.19 (2,) 70.24 17.18 0.64 - - J. W. L. The Dachberg, a Volcano of the Rhone.By F. RINNE (Jahrb. f. Min., 1888, ii, Ref., 406-407, from Jahrb. preuss. geol. Landesanst., 1886, 1--22).--Near Rasdorf on the Rhone is situated the Dachberg, on the summit of which is an unniistakeable crater. The unaltered basalt at the edge of the crater is a dense, glassy felspar-basalt, con- sisting of plagioclase, augite, olivine, magnetite, biotite, and apatite. The chemical composition of the basalt is as follows:- SiO,. TiO,. A1,03. Fe203. FeO. MnO. MgO. CaO. Na20. 41.71 3.51 15.80 5.59 7-64 0.16 4.85 10.30 6 . ~ 8 K,O. Li,O. SO3. C1. H20. COP P205. Total. Sp. gr. 1.00 trace 0.12 0.46 2.22 2-01 trace 101.45 2.90 B. H. B. Dolerite of Londorf. By A. STRENG (Jahrb. f. Mirt., 1888, ii, Ilem., 181-229).-The author has made an exhaustive mineralogical nud chemical investigation of the typical dolerites of the Vogelsberg.The dolerite of Londorf, to which he has principally directed his at tention, has the following percentage composition :- SiO,. Ti02. Al,O,. Fe,O,. FeO. CaO. MgO. K,O. 49-08 1-82 13.43 6-49 5.92 8.92 9-58 1-00 Na20. P2O5. H,O. Total: 3.42 0.51 0.32 100.49 From analyses of its constituents, the dolerite is calculated to be composed of 1-18 per cent. of apatite, 56.01 per cent. of andesine, 7980 per cent. of augite, 20.11 per cent. of olivine, and 3.10 per cent. of magnetite and titaniferous iron ore. B. H. B. Porphyrites at Gabian. By P. DE ROUVILLE and A. DELAGE (Cornpt. rend.. 10 7, 663-667) .-Near Gabian in HBrault there is a, dyke which runs north-east and south-west and consists of two porphyrites.One of these, which is by far the more abundant of the two, cuts through Silurian, devonian, and carboniferous beds without producing any noteworthy metamorphism, and then penetrates into coal-MINERALOGICAL CHEMISTRY. 111 measures which have undergone somewhat profound alteration. I t follows that this dyke was formed after the deposition of the coal- measures, and the fact that pebbles in the overlying permian con- glomerate consist of the material of the dyke, shows that it was formed before the deposition of the permian beds. This dyke is not homogeneous : it contains apatite, zircon, magnetite, oligoclase, black mica, orthoclase, amorphous matter, chlorite, calcite, damourite, and quartz. The second porphyrite forms isolated masses in the main dyke, and is of later formation than the lower permian, since the latter beds are somewhat altered where they come in contact with the dyke.It contains large crystals, the nature of which could not, be determined, well developed and distinct microlit,hs of labradorite, magnetite, augite which has to a great extent been converted into chlorite, calcite, chlorite, damourite, quartz, and ferruginous products of decomposition. C. H. B. Composition of the Serpentine Rocks of Colle di Cassi- moreno and Monte Rsgola. By c. MONrEMARTINI (Gnzaetta, 18, 103--112).-At Colle di Cassimoreno and also in the neighbourhood of Monte Ragola, Chistoni found isolated masses of serpentine rock exhibiting strong magnetic polarity. The author is indebted to him for the two specimens he has examined.The serpentiue of Colle di Cassimoreno is massive and compact; of brecciated and porphyritic appearance, witb lustrous, lamellar crystals of enstatite (bronzite) disseminated through the dark-green ground- mass. Besides these crystals, diopside and picotite also occur, together with magnetite, which forms one of the principal constituents of the rock. The hardness of the ground-mass is 6.5 and the sp. gr, at 13" varies from 2.73 to 2.76. The powdered rock is ash-grey in colour, and like all serpentine rocks has a marked alkaline reaction. Heated in contact with the air, it assumes an ochreons tint. It is partly decomposed by the action of hydrochloric or sulphuric acid, with separation of gelatinous silica ; the nnattacked portion consists principally of the crystals of enstatite and picotite.The rock on analysis gave the following results :- Loss on SiOz. Alz03. Fe,OJ. FeO. CaO. MgO. ignition. Total. 41-19 2.77 4.03 4.33 2.32 34-03 10.13 98% The enstatite, separated as far as possible from the other constituents of the rock, was analysed, and the results are given under I. In I1 the composition of the lherzolite from Germagnano in Piedmont is given for comparison :- Si02. AlZO3. FeO. CaO. MgO. H,O. Total. I. 50.65 3.05 7.99 1.68 31-49 2.78 99-59 11. 52.19 2.15 8.85 2.96 31.84 1.77 '39.76 These results show that the enstatite is bronzite.I1 2 ABSTRACTS OF CHEMICAL PAPERS. The rock therefore consists of a serpentine formed by the decompo- sition of peridote togcther with enstatite, diopside, magnetite, and other minerals ; this is also borne out by the microscopical and optical examination, full details of which are given.The rock also contains olivine, diallage, and amphibole. The sample of rock from Monte Ragola, which was from the rock mass of the mountain itself, had no magnetic polarity, and was quite different in appearance from the one just described. The ground-mass is light-peen w i t h dull-green nodules dissemi- nated in it ; these cau easily be separated, and on examination were found to consist- of altered bastite. A microscopical examination showed thatl the rock had all the characters of a serpentine formed by the alteration of a pyroxenic mineral. Neither the enstatite, diop- side, nor spinelle which characterise the Cassimoreno serpentine could be discovered in it.Its sp. gr. at 14" is 2.54. The analyvis gave the following results :- Loss on SiO,. Al,O,. Fe,O,. FeO. CaO. MgO. ignition. Total. 39.18 3.65 '7.26 1.55 0.42 34.79 12.81 99.66 Chromium, nickel, and manganese were also detected. C. E. G.MISERALO GIC A L CHE 111 S T R Y .M in e r a1 o g i c a 1 C h e m i s t ry.109Native Platinum from Canada. By G. C. HOFFMAN (Jahrb. j :Xin., 1888, ii, Ref., 386, from Geol. Szcrv. Can. Rep., 2, 5).-Nativeplatinum has been found with gold in several rivers in BritishColumbia. From the bed of Granite Creek, a tributary of t h eSixnilkameen river, grains were obtained varying in diameter froin1 to 4 inm., and weighing altogether 18.266 grams. The materialwas separated into a magnetic (1) and a non-magnetic portion (H), thecompositions of which were as follows :-Pt.Pd. Rh. Ir. Cu. Fe. OsIr. Chromite. Total.1. 78-43 0.09 1.70 1.04 3-89 9.78 3-77 1-27 99.9711. 68-19 0.26 3-10 1.21 3.09 7.87 14-62 1.95 100.29The sp. gr. of the magnetic portlion was 16.095, and that of theThe Pyroxenites of Morbihan. By C. BARROIS (Jahrb. f. Nin.,1888, ii, Ref., 413-414, from Ann. SOC. ge'ol. du Nod, 15, 69-96).-The pyroxenites of Morbihan form beds 0.1 to 2 metres in thick-ness in gneiss and mica-schists of Archean age. The main con-stituent of these rocks is a pale green augite of the fol1owi:igcomposition :-non-magnetic portion 17.01. B. H. B.SiO3 CaO. MgO. Fe20,. Al,O,. Na,O. K,O. Total.51.5 24.3 11.9 8.3 5.0 1.1 trace 102.3The augite is accompanied by zircon, titanite, and apatite in smallquantities, by garnet and idocrase in varying amounts, and by quartzgrains associated with felspar.Irregular grains of orthoclase onlyoccur in certain beds, and microcline is also of exceptional occurrence.A fibrous actinolite is, ho wever, present inlarge quantities, in many casesreplacing the augite, so that rocks resembling nephrite are produced.Titaniferous iron ore and ferric hydroxide are also present. By t h evariety of the character and relative proportions of the constituents,numerous distinct types are distinguished, which may occur in thesame bed. The author regards these pyroxenites as metamorphiclimestones. B. H. B.Riebeckite, and the New Formation of Albite in GraniticOrthoclase. By A.SAUER (Chem. Centr., 1888, 1128, from Zeit.deut. geol. Gess., 40, 138--152).-A new member of the hornblende-granite group has been found by the author in Socotra. This horii-blende, named riebeclzite, has the same composition as arfvedsonite,arid is the analogue of agirin of the augite series. From the analysis(No. 1 below) the formula 5FeSi0,,4Na&3i0,,5Fe,Si3O9 has beencalculated110 ABSTRACTS OF CHEMICAL PAPERS.The Socotra granite is much disintegrated, and the author wasthus enabled to examine more completely certain interchanges in thegranitic orthoclases. The microscopical examination showed anopalescence from the edge towards the centre of the crystals, occa-sioned by the formation of albite, the crystals having been originallyperfectly clenr and without inclosures.The following are tlteanalyses of riebeckite (1) and the secondary albite (2) :-SiOP Al,O,. Fe,03. FeO. MgO. MnO. CaO. Ntx20. K,O.(1.) 50.01 - 28.30 9-87 0.34 0.63 1-32 8-79 0.72- - 6.86 5.19 (2,) 70.24 17.18 0.64 - -J. W. L.The Dachberg, a Volcano of the Rhone. By F. RINNE (Jahrb.f. Min., 1888, ii, Ref., 406-407, from Jahrb. preuss. geol. Landesanst.,1886, 1--22).--Near Rasdorf on the Rhone is situated the Dachberg,on the summit of which is an unniistakeable crater. The unalteredbasalt at the edge of the crater is a dense, glassy felspar-basalt, con-sisting of plagioclase, augite, olivine, magnetite, biotite, and apatite.The chemical composition of the basalt is as follows:-SiO,.TiO,. A1,03. Fe203. FeO. MnO. MgO. CaO. Na20.41.71 3.51 15.80 5.59 7-64 0.16 4.85 10.30 6 . ~ 8K,O. Li,O. SO3. C1. H20. COP P205. Total. Sp. gr.1.00 trace 0.12 0.46 2.22 2-01 trace 101.45 2.90B. H. B.Dolerite of Londorf. By A. STRENG (Jahrb. f. Mirt., 1888, ii,Ilem., 181-229).-The author has made an exhaustive mineralogicalnud chemical investigation of the typical dolerites of the Vogelsberg.The dolerite of Londorf, to which he has principally directed hisat tention, has the following percentage composition :-SiO,. Ti02. Al,O,. Fe,O,. FeO. CaO. MgO. K,O.49-08 1-82 13.43 6-49 5.92 8.92 9-58 1-00Na20. P2O5. H,O. Total:3.42 0.51 0.32 100.49From analyses of its constituents, the dolerite is calculated to becomposed of 1-18 per cent.of apatite, 56.01 per cent. of andesine,7980 per cent. of augite, 20.11 per cent. of olivine, and 3.10 per cent.of magnetite and titaniferous iron ore. B. H. B.Porphyrites at Gabian. By P. DE ROUVILLE and A. DELAGE(Cornpt. rend.. 10 7, 663-667) .-Near Gabian in HBrault there is a,dyke which runs north-east and south-west and consists of twoporphyrites.One of these, which is by far the more abundant of the two, cutsthrough Silurian, devonian, and carboniferous beds without producingany noteworthy metamorphism, and then penetrates into coalMINERALOGICAL CHEMISTRY. 111measures which have undergone somewhat profound alteration. I tfollows that this dyke was formed after the deposition of the coal-measures, and the fact that pebbles in the overlying permian con-glomerate consist of the material of the dyke, shows that it wasformed before the deposition of the permian beds.This dyke is nothomogeneous : it contains apatite, zircon, magnetite, oligoclase, blackmica, orthoclase, amorphous matter, chlorite, calcite, damourite, andquartz.The second porphyrite forms isolated masses in the main dyke, andis of later formation than the lower permian, since the latter bedsare somewhat altered where they come in contact with the dyke. Itcontains large crystals, the nature of which could not, be determined,well developed and distinct microlit,hs of labradorite, magnetite,augite which has to a great extent been converted into chlorite, calcite,chlorite, damourite, quartz, and ferruginous products of decomposition.C.H. B.Composition of the Serpentine Rocks of Colle di Cassi-moreno and Monte Rsgola. By c. MONrEMARTINI (Gnzaetta, 18,103--112).-At Colle di Cassimoreno and also in the neighbourhoodof Monte Ragola, Chistoni found isolated masses of serpentine rockexhibiting strong magnetic polarity. The author is indebted to himfor the two specimens he has examined.The serpentiue of Colle di Cassimoreno is massive and compact; ofbrecciated and porphyritic appearance, witb lustrous, lamellar crystalsof enstatite (bronzite) disseminated through the dark-green ground-mass. Besides these crystals, diopside and picotite also occur, togetherwith magnetite, which forms one of the principal constituents of therock. The hardness of the ground-mass is 6.5 and the sp.gr, at 13"varies from 2.73 to 2.76.The powdered rock is ash-grey in colour, and like all serpentinerocks has a marked alkaline reaction. Heated in contact with theair, it assumes an ochreons tint. It is partly decomposed by theaction of hydrochloric or sulphuric acid, with separation of gelatinoussilica ; the nnattacked portion consists principally of the crystals ofenstatite and picotite. The rock on analysis gave the followingresults :-Loss onSiOz. Alz03. Fe,OJ. FeO. CaO. MgO. ignition. Total.41-19 2.77 4.03 4.33 2.32 34-03 10.13 98%The enstatite, separated as far as possible from the other constituentsof the rock, was analysed, and the results are given under I. In I1the composition of the lherzolite from Germagnano in Piedmont isgiven for comparison :-Si02. AlZO3. FeO. CaO. MgO. H,O. Total.I. 50.65 3.05 7.99 1.68 31-49 2.78 99-5911. 52.19 2.15 8.85 2.96 31.84 1.77 '39.76These results show that the enstatite is bronziteI1 2 ABSTRACTS OF CHEMICAL PAPERS.The rock therefore consists of a serpentine formed by the decompo-sition of peridote togcther with enstatite, diopside, magnetite, andother minerals ; this is also borne out by the microscopical and opticalexamination, full details of which are given. The rock also containsolivine, diallage, and amphibole.The sample of rock from Monte Ragola, which was from the rockmass of the mountain itself, had no magnetic polarity, and was quitedifferent in appearance from the one just described.The ground-mass is light-peen w i t h dull-green nodules dissemi-nated in it ; these cau easily be separated, and on examination werefound to consist- of altered bastite. A microscopical examinationshowed thatl the rock had all the characters of a serpentine formed bythe alteration of a pyroxenic mineral. Neither the enstatite, diop-side, nor spinelle which characterise the Cassimoreno serpentine couldbe discovered in it. Its sp. gr. at 14" is 2.54.The analyvis gave the following results :-Loss onSiO,. Al,O,. Fe,O,. FeO. CaO. MgO. ignition. Total.39.18 3.65 '7.26 1.55 0.42 34.79 12.81 99.66Chromium, nickel, and manganese were also detected.C. E. G