Localities of Minerals. 79 



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

 Tilar, 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 qnan- 

 tities of beautiful garnets j 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 tliem as are not so much 

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



the trapezoidal of Haiiy. 



5. 



if 



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. 



tif alo 



turnpike. 



6. White avgiti 



7. Talc, similar 



ty 



cinit}^f 



occurs in serpentine, accompanied by chromiferous oxide of iron, 

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



pike. Talc^ white, green, brownish red and reddish purple, occui-s 

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

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

 Cooptown, Harford county, Md- where it occurs In abundance, in 

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

 have never seen a descripdon 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 tlic color of tlie streak. It is translucid or semi-transparent, in 

 very thin nieces ; the surface has a smooth comnact aDnearance, 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 

 weU. 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 luile west of the 13 mile stone on York turnpike 

 road, five inches long and two and a half broad, (perihexatdre of Hatty.) 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 hcxahedral prism. 



