66 



POPULAR SCIEKCE NEWS. 



[May, 1SS9. 



IRON PYRITES, OR FOOLS' GOLD. 



It is a common experience with chemists 

 to have brought to tliem for examination, a 

 package containing some crystals of a yellow 

 color, which the finder confidently believes 

 to be gold. The story of the man who 

 brought a sample to Dr. Jackson for examina- 

 tion, after he had married the widow "who 

 owned a whole hill of it," instead of before, 

 is well known, and his unfortunate experience 

 serves to illustrate the old proverb that "all is 

 not gold that glitters." 



Iron pyrites (pronounced, according to the 

 best authorities, pi'-rites) is common every- 

 where, and sometimes — but not often — really 

 does contain a trace of gold, although usually 

 it is entirely worthless. 



It is, chemically considered, a disulphide 

 of iron, Fe S^, containing, when pure, 46.7 

 per cent, iron and 53.3 per cent, sulphur. 

 Unlike gold, it is one of the most abundant 

 substances, being found in nearly every geo- 

 logical formation, and 

 in every part of the 

 world. It has proba- 

 bly been formed from 

 sulphate of iron, by the 

 action of organic mat- 

 ter, which has removed 

 all the oxygen, or, in 

 other words, reduced 

 it to a sulphide. It is 

 very hard, being but 

 little inferior to quartz 

 in this respect, and 

 will strike fire with 

 steel, like Hint ; hence 

 the name of pyrite — 

 fire-stone. In this re- 

 spect it is quite unlike 

 native gold, which is 

 very soft. Its lustre is 

 brilliant and metallic. In color it varies 

 somewhat, — sometimes it is pale yellow 

 and closely resembles brass, at other times 

 it has the color of gold, and sometimes 

 it is brown or gray. In fine powder it is 

 brownish black, and leaves a black streak on 

 rough porcelain or honestone. 



Pyrites is generally found crystallized ; gold, 

 very rarely. Large and fine crystals of py- 

 rites have been found iji Colorado and on the 

 Isle of Elba. In limestones and slates, small 

 crystals are frequently met with. The crys- 

 tals are usually cubes, which are frequently 

 striated in a peculiar manner, so that the 

 lines on sany two adjacent faces are never 

 parallel. A very characteristic form of crys- 

 tal, although much rarer than the cube, is 

 one bounded by twelve pentagonal faces, with 

 or without three smaller faces on eight of the 

 corners. Another very interesting form of 

 crystal is bounded by twenty triangular faces. 

 This last is the result of combining a dodeca- 

 hedron with an octahedron. It also forms 



curious twin crystals, one of which is known 

 as the iron-cross, and looks as if one cube had 

 been pushed into and through the other one. 



The principal use of ii'on pyrites is in the 

 manufacture of sulphuric acid, but in England 

 sulphur is also made from it. It frequentl)' 

 contains arsenic, which then passes into the 

 acid made from it. Sometimes it contains 

 selenium, which is then found in the slime on 

 the floor of the leaden chambers. As an ore 

 of iron it is practically useless, owing to the 

 great difficulty of removing the last traces of 

 sulphur and other injmious substances. Slaty 

 clay, w^hich contains much pyrites, is used for 

 making alum, for, by simplv roasting and 

 exposing to the air in a moist state, sulphates 

 of aluminum and iron are formed, which need 

 only the addition of an alkaline chloride, 

 such as ammoniinn or potassium, to convert 

 it into alum and remove the iron. 



Pyrites sometimes contain gold, and those 

 found in gold-bearing districts should alwa\ s 



be tested for the precious metal. There is no 

 characteristic by which gold-bearing pyrites 

 are readily distinguished from the ordinary 

 sort, and, when there is sufficient reason to 

 suspect the presence of gold, the ore shoidd 

 be submitted to a competent assayer for exam- 

 ination, since a paying quantity of gold could 

 easily escape detection by a less experienced 

 person. The reduction of the gold in pyrites 

 is attended with manv difficulties, but they 

 are daily being overcome in practice. 



Before closing, we would mention the fact 

 that there are several other kinds of pyrites 

 beside iron pyrites. There is also another 

 disulphide of iron, with the same composition 

 as the one described, but lighter in color, 

 called Marcasite. It cyrstallizcs in the tri- 

 metric system, but also occurs in globular, 

 reniform, and other imitative shapes, resem- 

 bling petrified fruit, and massive. It is much 

 less common than the cubical or yellow pyrites. 



Glance-cobalt contains arsenic and cobalt, 

 as well as iron and sulphur. In crystalline 



form it is very like the iron pyrites, but in 

 color lighter, with a faint shade of pink. It 

 is quite rare, being found chiefly in .Sweden. 

 Alispickel, also called arsenical pyrites, is of a 

 steel-gray color,very hard, and crystallizes in the 

 same form as marcasite. It contains about 40 

 40 per cent, of arsenic. It is found in Sweden, 

 the Hartz Mountains, and this country. 



Copper pyrites is a compound of sulphur 

 with iron and copper. It is much softer and 

 of a darker color than iron pvrites, and often 

 exhibits raijibow tints. Good crvstals are not 

 common, and the surface is usually irregular 

 or conchoidal. It is a valuable ore of copper. 



All kinds of pyrites are attacked by strong 

 nitric iicid with the evolution of red fumes ; 

 gold is not. The odor of burning sulphur, 

 and sometimes of arsenic, when stronglv 

 heated, also distinguishes pyrites from the 

 precious metal. 



BUTTERFLY DECALCOMANIA. 

 Now that the season of butterflies is nearly 

 at hand, some direc- 

 tions for transferring 

 the beautiful colors of 

 tlieir wings to paper 

 so that they can be 

 preserved indefinite- 

 Iv, may be of interest. 

 The process is a very 

 simple one and only 

 needs a little care and 

 practice to obtain 

 most satisfactory re- 

 sults. 



The color of the 

 wings of butterflies 

 is, as is well known, 

 due to minute scales 

 with which they are 

 covered, like the body 

 of a fish. These 

 scales are very loosely attached and are 

 rubbed ofl" at the slightest touch, as e\ery 

 one knows who has ever handled a butter- 

 fly. For this reason they can easily be 

 transferred to paper, porcelain, glass or other 

 substances, by a process almost exactly simi- 

 lar to that used in transferring decalcomania 

 pictures. 



Having obtained a suitable specimen, the 

 wings must be carefully separated from the 

 body with a pair of fine scissors. A solution 

 of the best gum arable must be previously 

 prepared, to which is added a little sugar, a 

 little salt, and a little alum. This mucilage 

 should be of the consistency of a very thin 

 syrup. Then with a camel's-hair brush spread 

 it thinly over the paper so as to roughly form 

 the outline of the space to be occupied by the 

 wings (No. I.) The wings may be arranged 

 either open or closed (a, b. No. 3) but space 

 must be left for the body to be painted in 

 afterwards. The wings are then carefully 

 placed in position upon the mucilage, and, if a 



