90 Scientific Intelligence — Mineralogy. 



April 28, p. 131). — The crystals of diopside were from a Swedish 

 furnace at Gammelbo in Westmannland. They are two or three lines 

 long ; translucent or transparent ; grayish, pearly, to greenish or red- 

 dish gray. 



G. = 3-127; H. = 6; composition — 



Si Al Mg Ca Fe Mn Na K 



54-69 1-54 15-37 23-56 008 1-66 1-94 1-15 = 100 



corresponding to the general formula, Ki 3 Si 2. 



The molybdate of lead was found in a reverberatory furnace at 

 Bleiberg in Carinthia, in crystals very much like the natural crys- 

 tallisations. 



9. Formation of Arragonite, C 'ale-spar, Brochantite, and Mala- 

 chite. — M. Becquerel some time since shewed that calc-spar may be 

 obtained in primary rhombohedrons, through the slow reaction of a 

 solution of bicarbonate of soda, feeble in degree (2°), on laminae of 

 sulphate of lime or gypsum. On experimenting with a solution 

 marking five or six degrees, the carbonate of lime crystallised in the 

 trimetric system, or in other words as arragonite. It is hence not 

 surprising that arragonite should be found in gypseous and saliferous 

 deposits, like those of Spain, Salzburg, and elsewhere. 



Calc-spar may also be obtained by the action of a solution of 

 potash marking 10°, on gypsum, the solution being contained in a 

 flask imperfectly closed. In this case the carbonic acid is derived 

 from the atmosphere. 



Brochantite (subsulphate of copper) is easily obtained, looking 

 like native specimens, by putting a piece of porous limestone in con- 

 tact with a saturated solution of sulphate of copper. The Brochantite 

 is deposited upon the limestone in small crystalline tubercles along 

 with the crystals of gypsum. 



Malachite (Cu C + Cu H) may be obtained by the reaction of 

 coarse porous limestone on a solution of nitrate of copper, marking 

 12° or 15°, and when the action ceases, by plunging the mass into 

 a solution of an alkaline bicarbonate marking 5° or 6°. The piece of 

 limestone in the first case becomes covered with subacetate of copper ; 

 and this subacetate, in the next step, changes to malachite, or if 

 prolonged, to a double carbonate of copper and soda. The mala- 

 chite is in small silky globules. 



10. On the Artificial Formation of Malachite ; by M. Henri 

 Rose (Konigl. Preuss. Akad., Oct. 1851). — When a solution of 

 sulphate of copper is precipitated in the cold by carbonate of soda 

 or potash, the precipitate is at first voluminous, and of a blue colour ; 

 but left for a while and then washed, it becomes more dense and of 

 a green colour. It has the composition of green malachite as found 

 in nature. 



