Ford and Bradley — Margarosanite. 159 



Art. XXI. — Margarosanite, a New Lead-Calcium Silicate 

 from Franklin, JV. J. ; by W. E. Ford and W. M. Bradley. 



The new mineral to be described in the following paper was 

 originally observed on specimens from Franklin, 1ST. J., that 

 came from about the 1000 ft. level of the Parker shaft on 

 North Mine Hill and were collected during the year 1898. It 

 was partially investigated by S. L. Penfield and C. H. Warren 

 during their study of Franklin minerals which resulted in the 

 description of the other new species, hancockite, glaucochroite, 

 nasonite and leucophcenicite.* Partial analyses were made by 

 both Penfield and Warren, but the investigation was never 

 carried to a conclusion and the results obtained were not pub- 

 lished. Their material has remained in the Brush Mineral 

 Collection since that time and was added to several years ago 

 by a few more specimens presented by the Foote Mineral Co. 

 of Philadelphia. It is only recently that a complete and satis- 

 factory investigation of this mineral has been possible. The 

 results have shown that we have here another new species to 

 add to the already long list of those peculiar to the Franklin 

 locality. 



Margarosanite, as the new mineral is called, is a silicate 

 essentially of lead and calcium. It occurs in lamellar masses 

 composed of thin plates packed closely together and which in 

 general show a rhombic outline due to cleavages. It is color- 

 less and transparent, showing a distinct pearly luster. It has 

 a hardness of 2 - 5-3 ; specific gravity of 3 - 991. In the oxidiz- 

 ing flame it fuses with some difficulty, the fragment assuming 

 an amethyst color, but in the reducing flame, it fuses easily and 

 quietly at about 2 to an opaque grayish glass. In the reducing 

 name it gives a pale azure-blue flame with an outer border of 

 pale green. With fluxes on charcoal it gives a metallic globule 

 of lead accompanied with the lead oxide coating. It gives the 

 characteristic color tests for manganese when fused in the 

 sodium carbonate or borax beads. It is decomposed by treat- 

 ment with nitric acid, yielding separated silica. 



The mineral shows three good cleavages. The principal 

 cleavage is parallel to the tabular development of the mineral 

 and is so perfect that it almost gives a micaceous character to 

 the material. There are two other well-developed cleavages 

 which are nearly, but apparently not exactly, perpendicular to 

 the first. These are shown by the characteristic rhombic out- 

 lines of the broken plates of the mineral and by the numerous 

 cleavage cracks existing within the sections. The traces of 

 these latter cleavage directions upon the surfaces of the plates 

 make angles with each other which are closely approximate to 

 102° and 7S°. On a few of the plates an oblique terminal edge 

 * This Journal, viii, 339, 1899. 



