Professor Breithaupt ow Russian Platina Sand. 273 



magnetic, others not ; hence these two kinds are probably va- 

 rieties of two distinct species. 



First species : Commcm Platina. — It is the same with the 

 platina brought from America by Humboldt, and possesses the 

 following characters : 



Colour platina-gret/^ which is different from steel-grey. On 

 concave places there is observed a yellowish appearance. — The 

 grains are angular and bristled, seldom blunt-edged ; the crys- 

 tals are hexahedral, and grouped, as in silver-glance. — Hard- 

 ness = 70. — 8.5 *. Is perfectly malleable. Specific gravity 

 17.001 — 17,608. A large American specimen in the Werne- 

 rian cabinet was 16.914. It is well known that the native pla- 

 tina is always lighter than that prepared by chemical means. 



Second species : Ferruginous Platina. The colour is pZa- 

 tina^grey, but darker than in the preceding species. In hol- 

 lows in the specimens, the surface is tarnished, from dark-brown 

 to black, as in meteoric iron. The grains and crystals have the 

 same forms as in the former species. — Hardness = 8.0 — 8.5. 

 Malleable, but not so completely so as in the first species. Spe- 

 cific gravity 14.666 — 15.790. It is magnetic, and in some grains 

 not only repels, but also attracts. It is distinguished from the 

 former species by lower specific gravity, less perfect malleability, 

 and its affording, by chemical trials, a considerable portion of 

 iron. 



2. Gold.—l found few grains of gold in the platina-sand : 

 these were partly gold-yellow, partly greyish-yellow. Is Wer- 

 ner's greyish-yellow gold, gold combined with platina ? 



3. Irid-osmin. — This species, which is a compound of iri- 

 dium and osmium, presents the following characters : 



The colour is not steel-grey, as is generally believed, but a 

 middle colour, between whitish lead-grey and common lead-grey. 

 It occurs crystallized in low hexagonal prisms, which have an 

 axotomous cleavage. Hardness = 8.0 — 8.75. Is imperfectly 

 malleable. Specific gravity = 17.969 — 18.571. 



It would be desirable to have iridium and osmium again exa- 

 mined. Iridium will probably be found to possess a higher 



* Scale of hardness here used is that of Breithaupt, in his Mineralogy, 

 7 — that of glassy actynoite, 8 = that of adularia, 9 = quartz. 



JULY — SEPTEMBER 1827. S 



