Now, then, as to the distribution and occurrence of oil shales. The world over we have oil shales. Most of them are in comparatively thin depositsin many cases matters of inches separated from other and different character of geological formation by distinct lines. Oil shales are known to exist in most of the formations from the Ordovician to the present. In most places I say the oil shales are insignificant in quantity relative to the rest of the rocks. However, in Colorado and the Rocky Mountain region in general we have the immense deposits of oil shale of the Green River formation which is of the Eocene age. As I say, our earlier knowledge of that series of rock was very meager, and we have made some very funny looking statements when we think of them now from our present knowledge. We know now that in northwestern Colorado there are over 2,000 feet of oil shale in one mass body, all of which will yield oil in some quantity.

True, there are in that 2,000 feet thin portions which are very lean in oil yielding content. There may be thin partings of very sandy material, but if we are to define a limit between sand and shale a lot of our shale is sand and a lot of our sand is shale on any limit we might place. Our oil shales of Colorado in some places contain a very high percentage of silica. In still other good oil yielding shales the silica is so finely divided that it becomes almost a clay instead of a shale.

The richness of the Green River formation from top to bottom is quite variable but in lateral extent remarkably uniform. We have in this 2,000 feet or more of Green River formation a portion of the formation which we can classify as the richest part of the formation. It may be 500, it may be 200, just what you want to throw into that class of the richest part. We have leaner portions of the formation, but it is all oil yielding. Although I am not a mining engineer I have had a little experience in the examination of mines, both metal and coal, and I am not so sure but what we are going to mine an awful big thickness of the Green River formation in one vast mining operation, and if so we certainly will be able to practice conservation and economies which can not otherwise be touched.

To summarize then, as I see the subject before the department, the question of what constitutes discovery of oil shale, Oil shale by definition is a shale which will yield oil. There is no reason, excuse, or justice in attempting to put a minimum limit on oil yielding character into the definition of oil shale. We have immense deposits in the West which are subject to the mining laws. There have been vast areas taken up as placer locations, and, as Mr. Boatright mentioned, if those shale deposits are made available to the most economical and proper mining development we in Colorado and the United States in general will be at profit from many, many standpoints. I thank you.

Secreatry WORK. Mr. Winchester, may I ask a question? How much does a gallon of oil weigh-about? They do not all weigh the same I presume. Mr. WINCHESTER. Oils vary greatly in weight according to the character of the oil.

Secretary WORK. Between what limits? I know a gallon of milk weighs 8.8 pounds.

Mr. WINCHESTER. Oil is lighter than water. around 7 pounds to the gallon.

Water is about 8; oil will be

Secretary WORK. What do you figure on? Long ton or short ton?

Mr. WINCHESTER. All of my figures have been based on short tons. These figures given in the Scotch report are on the long ton and the English barrel. Secretary WORK. What is the probable conjecture of average per cent of oil to the ton in the richest field you are familiar with?

Mr. WINCHESTER. Do you rean oil shale?

Secretary WORK. Yes; in oil shale. That can only be an intelligent guess I understand.

Mr. WINCHESTER. I have not thought of it in the light of that, and I hesitate to guess.

Secretary WORK. Well, just one thing, to arrive at in my own mind the relative weight of a ton of oil and a ton of shale itself.

Mr. WINCHESTER. I say we have this question of the specific gravity of the shale the rock itself-and the specific gravity of the oil that you produce. Perhaps I should have mentioned the fact that oil shale does not contain oil but yields oil-it contains materials from which we produce oil.

Secretary WORK. Yes; I understand.

Mr. WINCHESTER. And the quality, gravity, and so forth, of the oil that we produce depends more possibly upon the way that we reduce it than the material which is in the shale originally.

Secretary WORK. There is no free oil in a ton of shale that would produce 90 gallons?

Mr. WINCHESTER. Practically not.

Secretary WORK. There is some evidence that before retorting

Mr. WINCHESTER. A very small amount was extracted by ordinary solvents. but the percentage is insignificant.

Secretary WORK. Thank you.

Mr. HAWLEY. Mr. Fred Carroll will now discuss the shale values in the Green River formation and some of the economic problems that are involved in the consideration of these deposits.

Mr. FRED CARROLL (Denver, Colo.). There are about 50 labeled specimens of oil shale here which were taken from the 429-foot section sampled by me recently. The numbers on the labels correspond to every fourth number shown in the log. These specimens are as nearly representative of the shales at the various horizons as it is possible to select them.

An examination of these specimens show that the texture of the shales vary greatly-much of it is neither typical oil shale or typical sandstone. At least one specimen-this large one (unlabeled) with the heavy black band of oil shale near the top changes to almost a pure sandstone at the bottom. It will be noted that it has no cleavage along bedding planes.

This is characteristic of the oil shales in many places. The sandstones are often integral with the shales, and when subjected to wide ranges of temperature these rocks decrepitate, but when exposed to ordinary weathering processes they disintegrate, the leaner laminae breaking down first; thus leaving the appearance of a parting along bedding planes. When the weathered surfaces have been completely removed this condition changes and the rocks are again integral.

My investigations of oil shale deposits of the Green River series have been of a general nature. As Mr. Winchester has given you a description of the geology and others to follow me will cover certain important phases relating to the matter to be presented at this hearing, I will try to confine my remarks chiefly to the occurrence of the oil shales and the relative values of the various horizons. The occurrence of these shales will be better understood if you will look at these photographs. Some of you are familiar with them no doubt. (Here the photographs were passed around,)

I also have an album here which contains about 30 enlarged photographs, the first few of which are airplane views showing the field in the neighborhood of Rifle and DeBeque in Colorado. The other photographs were taken for the purpose of showing more closely the structural conditions found in the field. The first photograph which I handed to you illustrates it very well.

I will not attempt to describe in some detail the changes in the Green River formation beginning at the Wasatch, which is the underlying formation, and ascending to the top of the Green River formation. There are some changes laterally, but for our purposes these are not important as the chief differences are in the thickness of the Green River formation.

Between Parachute and Roan Creeks, the top of the Wasatch formation is practically a horizontal plane 5,750 feet to 5,800 feet in elevation above sea level. On top of this formation are oil shales and some sandy oil shales up to 100 feet in thickness that show small amounts of oil upon distillation. Overlying this is about 90 feet of oil shale which yields from a substantial trace to more than 30 gallons per ton. This horizon is thought by some engineers to be the first which will come into commercial development.

Overlying this is from 700 to 800 feet of shales-some quite sandy-that vary in oil-yielding qualties from a substantial trace to as much as 50 gallons per ton. In this are many so-called beds which have been previously considered of commercial grade or discussed as of probable commercial grade.

This brings us to a point which now appears in the first photograph which I gave you-overlying this [indicating]-from this point upward-for 600 or 700 feet, occurs what is often referred to as the middle portion of the Green River series. This contains the highest grade oil shales of the entire Green River formation and presents the best advantages from a mining standpoint of any of the whole deposit. I will describe this somewhat in detail as it is shown in the first photograph which I gave you, and on which you will notice a mark in the margin. Following from this mark through the center part of the picture you will notice a bench, or apparent softening of the shale cliffs. This is what is commonly called the sandstone marker which shows in almost every part of the area covered by the Green River formation, So

far as I know it extends from Soldier Summit easterly into Colorado and from Colorado northerly into Wyoming. This so-called sandstone marker is a misnomer. This sandstone is calcerous or limy and is described by some mineralogists as an oolitic sand, or what was once oolitic sand. It yields oil from 5 to 20 gallons per ton and in many cases shows a thorough admixture of sands and shales. This deposit is usually discussed and its different parts described with relation to the sandstone marker.

Immediately, or directly underneath this marker there is about 50 feet of shales which average in oil yield from 28 to 35 gallons per ton. The 200 feet below this varies somewhat throughout the district. One hundred feet of it, at, least, will average around 14 gallons per ton for this depth.

The estimates that I have just given you are based upon work done by various engineers and in numerous parts of this district. I have recently completed, however, a sampling of a section of about 700 feet of the Green River formation in the vicinity shown in these photographs. This work was done very carefully, the weathered surface being removed, and then a continuous sample trench cut down through the cliffs. The samples were taken at short vertical intervals and a careful record made of the sample, the specific gravity, the gallons per ton, and a computation following of barrels of oil per acre. I will read some of these just to give you an idea of the relative values of the shales. By starting at the top, which corresponds to the top of the cliff or excarpment as shown in this photograph. Sample No. 1 sampled 1.7 feet in thickness, had a specific gravity of 1.97, made a yield of 32.8 galons of oil per ton. The computation there shows 3,545 barrels per

acre.

Question. Acre-foot.

Mr. CARROLL. That is per acre, 1.7 feet in thickness. No. 2, 52 feet; specific gravity, 2.3; oil yield, 11.6 gallons; and oil yield per acre of 4,500 barrels. No. 3, 5 feet; specific gravity, 2.09; 13.4 gallons; an oil yield per acre of 4,540 gallons.

Two hundred of these samples ran very much the same. I will read the summary for the 427.9 feet. Average specific gravity was 2.23; average cubic feet per ton was 14.35; average oil yield in gallons per ton was 15.8; aggregate tons per acre was 1,298,900; aggregate barrels oil yield per acre was 488,340; average tons per acre-foot, 3,035; average oil yield in barrels per acre foot, 1,141. This is the interval that I believe will be mined when shales come into production; other engineers think 700 feet in thickness will be mined; and in some parts of the district I believe that this 700 feet will make an aggregate yield of as much as 700,000 barrels per acre.

Mr. HAWLEY. Were there any barren intervals in that?

Mr. CARROLL. Not one. I could read them all. There were samples taken.

Mr. HAWLEY. All yielded oil?

some 300

Mr. CARROLL. One shows a trace; every other sample taken from the entire 700 feet shows an appreciable amount of oil, and in no case less than a gallon except the one which shows as a substantial trace.

Question. Designate the sample number.

Mr. CARROLL. The sample number is M-11, 5 feet. I can give it in the geologic column if you want it.

Early impressions of the occurrence of these shales were that the entire Green River formation consisted of a large number of oil-shale beds ranging from 3 to 9 feet, and that each of these beds is separated from the other beds by valueless material, whereas a more thorough study of the deposit has led to a different conception of this potential industry. Systematic samples such as I have described to you show that instead of thin separated beds of the major part of the upper half of the Green River formation, referred to as the middle portion, should be considered as one large mass of similar material, and will probably all be mined and treated in retorts. And it is not improbable that some of the leaner portions of this part of the formation will be dressed mechanically to separate the good from the very poor, and the former again mixed with the higher grade shales for retorting.

These conclusions are based upon results obtained from the samplings which I have just explained to you and which were made at numerous places over a wide area in different parts of this oil-shale district. The samples were taken from outcrops at the surface, after weathering had been removed, and represent vertical distances ranging from a few hundred to 2,200 feet,

and when correlated it is found that the difference in oil yield of similar horizons seldom exceeds 20 per cent.

I will read a part of a record of sampling which extends the one which I have given you. I will not atempt to read it all. It is in two parts. The sample records with the chemist's certificates attached are shown in all of them. This one starts well up toward the top of the mountain and covers 170.8 feet vertically.

Going on down we have 2.6 feet, 14 gallons; and 0.8 feet, 42 gallons. The last one is of a thin layer of high-grade shale high up in the formation. The others run from a gallon to 26 gallons and average about 4 feet in each sample. The long-section sample record offered here goes upward from the marker 255 feet and downward about 175 feet.

This record suggests-at least that portion of it referring to specific gravities that there is an inconsistency between the two factors fixed by the Land Department as a requirement for discovery and first promulgated in the Freeman-Summers case. In that case they say that we must have 6 inches of 15gallon shale to yield 750 gallons per acre-foot when near the surface or 1 foot of 15-gallon shale to yield 1,500 barrels per acre when deeper. To yield sufficient oil to meet these requirements shale would have to show a specific gravity of 3.19, which is 30 points higher than any oil shales which we have found and almost higher than the average of those shales yielding 15 gallons or more per ton. Therefore, if the requirement concerning quality is correct, the requirement concerning aggregate yield per acre-foot is wrong.

The average of those oil shales lying above those which I have just described and which have been sampled methodically yield an appreciable quantity of oil-at least a substantial trace.

Some portions are sandy. If the Secretary thinks it advisable we will bring in here samples representing the entire depth of 700 feet.

Secretary WORK. It might be advisable subsequently but not to-day, Mr. Carroll.

Mr. CARROLL. We have those samples here.

Secretary WORK. We are primarily interested in discovery, but a little laterbefore the hearing or afterwards-I would like to have you leave a few of them with us.

Mr. CARROLL. There are several hundred pounds of them.

Secretary WORK. We will let the Geological Survey take them.

Mr. CARROLL. We have them here. Some of them will prove interesting. We might get some of those samples out here and look at them.

Secretary WORK. All right. Could we set those out here during the recess so as not to delay the hearing?

Mr. CARROLL. Yes; I will finish and we can have that discussion just after

recess.

My studies of the deposit with a view to the mining of this convince me that there must be one of two methods employed. The one which probably deserves first consideration is the undercut caving method which Mr. Mitke will be able to explain to you very clearly; the other is the glory hole method which is being employed in mining large bodies of nonmetallic substances and is occasionally employed in mining metalliferous deposits. A notable example of the former is the lime quarry at Santa Cruz, California, and one of the latter the mines of the Mexico Corporation at Fresnillo, Mexico, where in each instance the actual mining cost, including overhead and all other items chargeable to mining is less than 25 cents per ton. We are now ready to offer these figures as an estimate, but mention them simply as an example to show the costs actually being made. Undercut caving is making possible costs for mining which are not greatly in excess of what is shown at the two mines mentioned. It may be that large mining operations in these oil shale will produce costs which are not greatly in excess of those which I have just given you. In any event one of these methods is sure to result in a cost per gallon of oil yield much less than any method designed to remove only a thin portion of the formation.

Mr. Mitke, who will follow me, will be able to tell you more concerning mine methods and costs, and explain why we must choose a method designed for the extraction of the large mass rather than to adopt the coal mining or selective method.

I thank you.

Secretary WORK. We would like to proceed with the next speaker.
Mr. HAWLEY. Mr. Mitke will be the next speaker on mining methods.

STATEMENT OF MR. CHARLES A. MITKE, CONSULTING ENGINEER, PHOENIX, ARIZ.
INVESTIGATION OF OIL SHALE DEPOSIT OF DEBEQUE AND GRAND VALLEY DISTRICT OF
COLORADO WITH REFERENCE TO METHODS OF MINING

The two principal problems which confront that operator of a mine are: (1) The method of mining, which is most suitable to the deposit, considering all the local conditions; (2) the metallurgy or treatment of the product after it is mined, in order that the metal may be used for commercial purposes. The cost of these two larger operations together with numerous small items must be low enough to yield a profit.

Recently I made an investigation of the oil shale deposits in the DeBeque and Grand Valley Districts of Colorado with special reference to methods of mining.

This deposit is extensive. By glancing at the map, it will be noted that the deposit is cut by a number of deep canyons exposing the outcrops for miles in many places, so that these outcrops may be carefully studied, sampled, and tested. The canyons happened to be so located as to expose large blocks of oil shales on several sides. This offered an opportunity for testing the formation, first, regarding its uniformity and second, the continuity of the strata, as it can be readily examined and some of it may even be studied on three sides. A large number of cuts have been made vertically across the formation from which average samples were taken and some attempts at quarrying have been made which exposed parts of the less weathered surfaces of the oil shale. Much valuable information has therefore been obtained from a study of these points as well as from determinations in the chemical laboratory.

General characteristics of a deposit.-Some of the outstanding features which are considered in the selection of any mining method are:

1. Shape and size of the deposit.

2. Thickness.

3. Hardness, toughness, texture, and so forth.

4. Breaking qualities as they apply to caving systems.

5. Standing qualities-extent rock will stand without timber.

Characteristics of oil shale deposit. The important features which would enter into the selection of a method of mining suitable to the oil shale deposit are the following:

First. Shape and size of the oil shale deposit. It is in the form of a thick blanket extending over an area of many square miles. An important fact is soon apparent to the observer, that the entire deposit lies almost horizontal throughout the district.

No faulting has been noticed anywhere in this field, which frequently presents costly problems in many deposits in foreign countries.

Second. Thickness of the shale formation.-This deposit is known as the Green River formation, and carries more or less oil bearing minerals about 2,600 feet in thickness. The logs taken at various places show that some horizons are very lean in mineral content, others are richer, and some parts near the center are called high-grade.

Third. Hardness, toughness, texture, etc.-Most of the rock in the entire shale bearing formation of the Green River formation series has what we call a medium hardness although there are certain sections in the mahogany zone which have characteristics resembling hard rubber. This latter zone, however, is only several feet thick.

Fourth. Breaking qualities as they apply to caring systems. In examining the weathered surface along the outerop it will be noted that the formation wherever exposed seems to have numerous so-called joint planes, or lines of weakness, which have a general vertical direction. When the rock is broken it usually breaks up along these lines of weakness in small pieces. This