The Nome daily nugget., 1911-04-06

lNe toliection ana museum or all the harder rocks and minerals in a region. and if a petrologist desires before ex- amining a district to gain a prelimin- ary idea of the rock it contains he can not do better than visit a typical placer ground especially one, as is of ten the case, formed at the confluence of several gulches or canyons coming in from different directions.
 The glaciers starting high up in the ampitheaters, near the tops of the mountains, and grinding their way down the tributary canyons mined everything in place they came across and carried both the minerals and de- bris matter on their backs and within their mass down to the placer. These materials consist mostly of the harder rocks and most indestructible mineral. The softer rocks are ground into gray el or washed into pebbles and sand by the subsequent steams and torrents that followed after the glaciers in melt ing. In the various chemical processes going on within the placer, and with the aid of vegetable and mineral sa:ts. the soluble minerals, such as silver and lead are commonly dissolved away. leaving no trace, whilst the gol and large variety of hard and insoIuble minerals remain. Amongst these is the so-called black sand or magnetic iron. This is probably an altered re7tdun1 from the masses of pyrite originall.. containing gold and brought down srora the vein and from other iron-ba ,~'ng minerals in the rock. This so .calle:, satd. which may contain at times p,t bles of magnetic, several inches in diameter. and several pounds in weight. may contain 8 certain amount of gold within its mass. In other cases it is a troublesome element in dredging and placer mining because if superabund- ant it is liable to carry the gold with 1t over the plates without giving it a chance to settle and amalgamate If this sand is in quantity and is saved, being commonly pure magnetic, it may have it's value in iron smelting or in other metallurgical processes in which iron is used.
 large and varied collection of hard and soluble minerals found in rocks of various kinds, sometimes as consti- uents of them, are concentrated in the placer by the sorting power of water and are often recovered in the clean ups, such as garnets, rubies, beryls.. corundum, topaz. tourmaline and long list of gem stones even to the diamond. With these may be cetrain valuable indestructible minerals such as grains of platinum. iridium, tantaium and oth- CT rare metals and minerals. The com mercial platinum of the world has so far been: obtained from placers, espe- cially those in the Ural mountains of Russia. Placers on the Pacific coast have been repeatedly found to con tain platinum. even in commercial quantities. Tin in Cornwall was for a long time obtained from placers or w st were termed "su cam woi kings and fin Batavia. Borneo and ota.t m bearing Islands of the Pacific tin oc- CUTS in surface deposits or placers. As many of these minerals and gems are of commercial value. 1t behoo~es the placer miners to look we'll to their cleanups and save whatever they think may be of value
 We are indebted to the discoverer of Leadvilie to the cleanups of the Cali fornia old placers in that region. The miners in their work frequently found what they call "heavy rock" which obstructed their rifles. and in conse- quence was contemptuously thrown on the dump This worthless and dls- carded heavy rock was recognized by a mineraiogist as carbonate of lead. and assays showed 1t to be rich in silver It was easily traced to it's source and the result was the present camp of Leadville. A placer not onipq provides samples of the rocks of a region. but may point to the source whence its gold was derived and in place. A par ticular rock observed 10 be conspicu- ousiy common in a placer is likely to be the rock in which the gold-bearing vein occurs. and 1t may not be diff ficuit to trace this rock to its place and there find the vein. It has often been remarked. however. that many rich placefs do not derive their gold from any large and rich concentration in uIace fin veins but from the breaking