Localities of Minerals. 79 



4. Precious garnets. — In granite, whose felspar is white and gran- 

 ular, two miles and one fourth from the city, N. E. of Jones' falls, 

 there are cuneiform masses of mica, from three to seven inches 

 broad, and some three inches thick at one edge, inclosing great quan- 

 tities of beautiful garnets; most of them seem to have, been com- 

 pressed between the plates of mica, into a tabular* form ; some are 

 not thicker than good writing paper ; in color they vary from cherry 

 red to brick red, with a vitreous lustre ; their breadth seldom ex- 

 ceeds two tenths of an inch. Such of them as are not so much 

 compressed, as entirely to conceal the crystalline form, appear to be 

 the trapezoidal of Haiiy. 



5. Common garnets, (primifif of Haiiy,) are found in great abun- 

 dance, the largest two inches in diameter and very perfect for large 

 crystals, in a decomposed mica schist, three miles east of Jessop's 

 mill, on the Gunpowder river. Common garnets, [primitif alonge of 

 Haiiy,) in mica slate, nineteen miles from this city, on the York 

 turnpike. 



6. White augite, formerly noticed, in this vicinity. f 



7. Talc, similar to that beautiful green variety of Smithfield, R. I. 

 occurs in serpentine, accompanied by chromiferous oxide of iron, 

 steatite, &z;c. four miles east of the 24 mile stone on the York turn- 

 pike. Talc, white, green, brownish red and reddish purple, occurs 

 in small scales, at locality 3 ; its lustre is pearly. 



8. Magnesian hydrate of silica. — This substance I met with near 

 Cooptown, Harford countj^, Md. where it occurs in abundance, in 

 serpentine ; and although it is said to exist in other places, yet, as I 

 have never seen a description of it, I shall submit the following. 

 The color, by reflected light, varies from dark chesnut brown to rather 

 dark honey yellow, but a shade of red is given to it by transmitted 

 light ; the powder feels rather gritty and is yellowish white ; this is 

 also the color of the streak. It is translucid or semi-transparent, in 

 very thin pieces ; the surface has a smooth compact appearance, and 



* I have constructed two electric needles, and capped their centres with these 

 garnets, instead of rock crystal, as recommended by Haiiy, and find they answer 

 well. Their natural polish is so perfect and their forms so beautiful, that they would 

 derive little embellishment from the jeweller. 



t I lately found a crystal, one mile west of the 13 mile stone on York turnpike 

 road, five inches long and two and a half broad, (perihexaedre of Haiiy.) I have 

 also found a crystal of the dark variety of augite, formerly noticed by Dr. Hayden 

 as being within the range of the white variety. It is a hexahedral prism. 



