THE PANNING TABLE
The Panning Table is usually 28 inches high by 30 inches wide by 60 inches long. It has two wash tubs on top. A safety pan is placed in the bottom of each tub. A shelf is directly under the table top to hold the dish for holding the concentrates. The grizzly pan and the regular pan are also part of the equipment for the panning table. The grizzly pan has three-eight-inch holes. This allows the small material to wash through, and speedily eleminates the coarse material.
The material is taken out of the volume bucket with the gold scoop and placed in the grizzly pan which is in the second pan. The pans are usually filled two-thirds full. The stones and large cuttings are washed clean while the small particles fall through the grizzly pan into the second pan. The rocks are looked over and examined for nuggets before thrown out and the rough panning is done in the first tub. The fine panning is done in tub No.2, where the water is clear. By having the water slightly warmed, the working conditions are more pleasant for the operator and also the clay tends to disintegrate more readily. The panner classifies the gold in one, two, and three colors. No.3 is the finest, and consists of all particles weighing less than 1 Mg; No.2 is gold consisting of all particles weighing between 1 Mg. and 4 Mg.; while No.1 gold is any particle weighing over 4 Mg. The colors are recorded in the log book. The concentrate is placed in a bottle, and marked with a Line Number, Hole Number, and Depth.
THE SAMPLE BOTTLES
For handling samples, some of the companies use small bottles similar to a vaseline jar. The cover is made of aluminum and of the screw type. The top of the cover is flat and has a dull finish, similar to a sand blasted surface. Writing with lead pencil is very legible on this type surface. The Line Number, Hole Number, Depth, and the panner's signature are all written on top of the bottle.
After all values have been recorded and the bottles are again sent out in the field, the writing is removed by a scouring action with the thumb, using sand and water. This method eliminates the danger of lost labels. Remember: reliable evidence inspires confidence in the crews' reports.
THE ROCKER
Directly beside the panning table is the rocker. The rocker, as used for checking drill samples, is very similar to the one used by the small individual placer operator. Some of the differences are: three-eight-inch holes in place of half-inch-holes in the punched plate; punched portion of plate only two-thirds of half size used in the ordinary rockers, preventing all the material from being washed through with the first dipper of water. As the rocker is cleaned up so often, only two or three riffles are necessary.
TREATMENT OF GOLD
A few of the operators take the bottles of concentrate from the hole, carefully pan them down as far as possible, dry them, remove the magnetic material with a magnet, blow the remaining black sand off and then weigh the gold.
The usual procedure is to use a six-inch gold pan, pan the material down to a high concentrate, and them amalgamate the gold. This is done by rubbing the black sand and concentrate with mercury, then carefully panning off the black sand. This is usually caught in another pan and checked to see that no values have been lost. The samples are then usually placed in bottles marked for future reference. At this time it is well to qualitatively inspect the contents of the pan and black sands for platinum or unusual amounts of any of the other valuable metals or minerals which are apt to be found in placer deposits.
There are times when the gold does not readily amalgamate, due to oil or grease from the sand pump, pipe joints, vegetation, et cetera. Adding a little caustic potash usually eliminates this trouble. To amalgamate the gold, some operators add one or two drops of dilute nitric acid to the amalgam and concentrates and stir vigorously was a glass stirring rod until all the gold has been absorbed by the mercury.
The ball of amalgam is then carefully placed in a porcelain annealing cup or test tube. Dilute nitric acid (specific gravity 1.42, plus an equal volume of water) is added to the cup and the contents heated over the flame of an alcohol lamp. The mercury goes into solution with the nitric acid, leaving the natural alloy of gold and silver. The acid should be heated only enough to accelerate the reaction. Excessive or continual heating will dissolve the alloy in the gold and change its fineness. This loss of weight may cause an error, as the values are computed on the basis of natural fineness of the gold. The mercury nitrate is carefully washed from the gold and silver alloy, using a wash bottle with hot water. After adding a drop or two of alcohol to the annealing cup to prevent sputtering, it is heated over the alcohol lamp to a red heat or to a point as hot as the lamp will allow. The operation removes the moisture and burns away any carbon or lint which would salt the weight of the gold. The gold is then weighed and values recorded in the log book.
LOGBOOK
An accurate systematic record should be kept of each hole drilled. Neat, accurate and carefully kept, and signed drillers logs are of the utmost importance and should be as carefully prepared as banking or legal papers. The reliability of a report on any placer deposit depends on the care with which the examination is conducted and recorded.
The driller and panner have a good opportunity to examine all the conditions relative to the deposit. All factors which may in any way have any bearing on the cost of the operation should he noted in the logs. Any corrections or compensation for lack of core should also be made in the field at the time, as later in the office, engineers might not fully understand all the conditions.
Explanations of Headings on Log Sheet
The following data is usually recorded on the log sheets:
- 1-Name of property
- 2-Location
- 3-Date
- 4-Line Number
- 5-Hole Number
- 6-Elevation
- 7-Time: Entries are made in this column of the time of day each pumping is made. At the bottom of the page the time consumed in drilling, pulling, moving, repairs, and delays is recorded. These records are helpful in determing the cost of prospecting similar ground.
- 8-Depth of the cutting edge of the drive shoe: The last item in this column is the total depth drilled.
- 9-Depth of pumping: Care must be taken to see that pumping is not continued farther than within two inches of the lower edge of the drive shoe until bedrock has been reached or when a boulder is encountered. Notation should always be made when drilling below the shoe.
- 10-Entries are made of each individual drive.
- 11- The rise of the core in the pipe for each drive: This is the distance from the bottom of the drive shoe to the top of the core.
- 12-Core after pumping: The amount of core left in the pipe is naturally less than before pumping. This is the distance from the bottom of the drive shoe to the top of the core and is termed the plug. It usually varies from two to four inches.
- 13- The length of core removed: The difference between the core before pumping and the core after pumping shows the rise of the core in the pipe. Some operators use this in computing the volume. Volume computed by this method is known as the core volume by pipe measurement.
- 14- Volume Bucket measurement. This is exactly as the name implies, the volume as measured in the volume bucket.
- 15-Classification of colors: The number of colors are classified in the No.1, No.2, and No.3 sizes. No.3 is the finest and consists of all particles weighing less than one milligram. No. 2 is the gold consisting of all particles weighing between one milligram and four milligrams. No. 1 gold is any particle weighing over four milligrams. These are recorded on the lines opposite the depths of drive, so that the various pay streaks will be known.
- 16-Estimated weight of gold: The panner becomes very proficient in estimating weight. He records the weight of the different colors in the log on lines corresponding with the depths at which they are found. This is helpful in following pay streasks.
- 17-Formation: The nature of the formation corresponding with the various depths is also noted. Very often the pay streak has a distinctive color. It is advisable to make a notation of this. The size and quantity of boulders have a definite bearing on how the property should be worked. Properties containing an unusual amount of clay require special washing equipment to prevent the clay from going through the boxes and picking up the gold. Some properties contain black sand which has a tendency to pack the riffles and decrease the amount of material which can be handled.
- Note from webmaster - #18 was missing in the original text
- 19-Depth and nature of over-burden: Very often the over-burden is removed by a different mehtod than that used for working of the gravel. Information such as buried logs, large boulders, etc., have a direct bearing on the cost, and records should be made of them.
- 20-Labor conditions, transportation facilities.
- 21-Depth of the pay gravel.
- 22-Depth to bed rock.
- 23-Nature of bed rock.
- 24-Depth of pay in bed rock.
- 25-Diameter of the drive shoe.
- 26- Theoretical volume of the core removed.
- 27-Measured volume.
- 28-Weight of gold in milligrams. (mg.)
- 29-Fineness of the gold.
- 30-Constant used in making calculations.
- 31- Value in cents per cubic yard.
- 32-Price of gold at which values were computed.
- 33-Signatures of the driller, panner and helper.
A list of abbreviations is included at the top of the log sheet which simplifies the recording.
Forms:
Drillers Field Log
Drilling Report
Summary Sheet
Factors for Determining Gold Value for Various Diameter Drive Shoes
Use of Hillman Multiplying Factors For Determining Gold Value Per Cubic Yard
Prospect Drilling Factors 1
Prospect Drilling Factors 2
