116 THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 
which has since been so metamorphosed as almost to have lost its original character. There is also 
a porphyritie slate, which consists of a fine-grained silicious base, with large crystals of feldspar 
scattered through it. These crystals are so large and so peculiarly distributed through the rock as 
to give it an appearance slightly suggestive of its being covered with hieroglyphics. For this 
reason, probably, it is known to the miners as “ China rock.” All these rocks have been irregu- 
larly and extensively decomposed, and are traversed in every direction by little seams of quartz, 
but they are not numerous. These seams are occasionally rich in gold ; but, to use the miners’ 
phrase, they are very “spotted.” It is said that about $81,000 has been taken from the French 
Claim, in ten or twelve years of working. There are several other claims of a similar character in 
this vicinity ; but none have paid so well as the French Claim. In the early days of California, 
the gulches and ravines about here are said to have paid quite well; but water is not abundant in 
this region. 
There are Seam Diggings between Johntown and Georgetown, on the hill at the head of Crane’s 
Gulch. They are in slate rock, which is quite taleose in character, and considerably decomposed. 
The slates have the usual northwesterly strike and nearly vertical dip, and are a good deal contorted. 
The seams of quartz are irregularly distributed through the slates, curving more or less, but on the 
whole following pretty nearly their stratification. The whole area of ground which has been 
worked here is not far from a quarter of an acre, and from the flume or tailing sluice to the top of 
the bank at the highest point is about seventy-five feet. At one place a bunch of quartz is ex- 
posed at a depth of about forty feet below the top of the bank, and is there nearly three feet thick ; 
but a few feet higher up it splits into eight or ten little irregular stringers which extend branch- 
ing upwards for a short distance and then disappear, none of them reaching the surface of the rock. 
This is, indeed, the case with most of the quartz seams at this locality ; they rarely extend to the 
surface. There has been a great deal of pyrites in the quartz as well as in the slates ; but it is now 
decomposed and carried away. The quartz itself is considered of little value and is not crushed, 
the gold being all obtained from the sluices, for which purpose the rock has to be blasted and 
broken with the hammer, and then washed with a two-inch hydraulic jet. 
§ 15. Amount and Yield of Gravel Worked. 
At Wiessler’s Claim, Iowa Hill, in 1871, the body of ground worked had a length of about 
1,200 feet and width of 400 approximately ; the maximum height of the bank was from 125 to 
130 feet. Assuming an average of 1,200 feet in length, by 350 in width, and 60 in depth, the 
amount of gravel washed away will be 933,333 cubic yards. The amount of gold taken out could 
only be guessed at. It was put all the way from half a million to two millions. 
From the southwest corner of the ground owned by Mr. Wiessler at Iowa Hill another large 
pit extends into the hill in a direction S. 30° E., magnetic, for a distance of 700 or 800 feet, with 
a maximum width of something over 200 feet, the height of the bank at the head of the pit rang- 
ing from sixty to eighty feet. The quantity of material removed from here was estimated at 
200,000 cubic yards. The bed-rock was not reached, and the gravel immediately upon it is said 
to be too poor to pay for working. No information was obtained as to the amount of gold yielded 
by this work. 
On the southeasterly side of the Iowa Hill Ridge, including the North Star and Sailors’ Union 
claims, an area of about 1,000 by 250 has been worked off, with an average depth of 100 feet : 
this gives, as the total amount of ground washed, about one million cubic yards. In regard to 
the operations of the Sailors’ Union Mine, the following statement was taken from the Company’s 
books. 
Ground worked : 580 feet long by 160 wide, and with an average depth of 116 feet. 
Amount of gold taken from the bed-rock . é : ; : ; 3 $124,598 
Amount of gold from gravel above the bed-rock . . . «. = . .° 42,800 
Total . . ~ wis s9 Sea 
