GEOLOGY. 331 



a short distance above and below the basal ridges, and the peculiarity of a 

 series of similar parallel planes, lying like plates one within the other is pre- 

 sented. The crystal is elongated in the direction of a line parallel with the 

 basal edges and thus becomes a regular octahedron. 



The length of the longer base is one inch, and the shorter seven-eighths of 

 an inch. I believe this to be the largest crystal ever reported ; it may be 

 called a skeleton crystal on a grand scale. 



Arborescent and Dendritic Gold Placer county. Some of the most remark- 

 able and beautiful specimens of gold ever seen, have been found at Irish 

 creek, three miles from Coloma. They simulate the veined and reticulated 

 appearance of leaves and more closely resemble the foliage of the Arbor Vitse 

 or the fronds of the most delicate ferns than of any other forms of vegetation. 

 The filamentous and arborescent masses are frequently united to plates (as 

 broad as the hand) which are covered with lines of crystallization and are 

 brilliant with numberless faces of partly formed crystals. They are also com- 

 bined with good crystals which are generally octahedral and have perfect 

 faces. I have a very beautiful specimen of this character in the form of a 

 leaf: one side is beautifully arborescent, and the other is studded with perfect 

 octahedrons of various sizes and about twenty-five in number, including the 

 smallest. They are geometrically arranged, all their similar edges being 

 parallel. This is believed to be the most remarkable and beautiful speci- 

 men known. Its weight is 17 pwt. 10 grains. Length, two and one quar- 

 ter inches, width, one and a hah inches. One of the foliated specimens 

 in my collection, bears a crystal having the form of a pentagonal dode- 

 cahedron with cavernous faces. One of the largest specimens of this arbor- 

 escent and foliated gold that has been procured, was about twelve inches 

 long and about four broad. A part of the specimen was a plate three or four 

 inches long, covered with triangular marks ; the remainder was arborescent, 

 and the whole appeared to have grown from one end. 



Another specimen slightly different in its character, and probably from 

 another locality in the vicinity, was ten inches long, three broad and about 

 half an inch thick. It weighed 31 ounces, and was free from quartz; form- 

 ing a most beautiful mass of a rich yellow color and a delicately marked sur- 

 face, consisting of a net-work of fibers. It appeared like a bundle of broken 

 fern leaves closely united together. These specimens are evidently from a 

 quartz vein, but although I have visited the locality, I have not been able to 

 see the place from which they were taken, or to obtain any reliable informa- 

 tion concerning their mode of occurrence and the associate minerals. Some 

 of the foliated specimens were incrusted with a thick scale of sesquioxyd of 

 iron. 



Native Copper and Red Oxyd of Copper. ~ftTien visiting Camp Tuma at the 

 junction of the Colorado and the Gala rivers, in December, 1853, several large 

 masses of superior copper ore were shown to me by the officers of the fort. 

 This ore was brought from the adjoining State of Sonora, Mexico, and the 

 vein is reported to be near Altar. It is within the limits of the strip of ter- 

 ritory recently acquired by purchase, and is therefore now in the United 

 States. Specimens are frequently brought hi by emigrants who cross the Col- 



