Butler USGS Professioanl Paper 144 pp 194-203

KEARSARGE LODE

HISTORY AND PRODUCTION

KEARSARGE FLOW

EXTENT AND CRITERIA FOR RECOGNITION

     The Kearsarge flow (pl. 40) has been recognized from Atlantic to Mandan, in Keweenaw County, a distance of about 35 miles. The rock is a well-developed ophite. The identification of this flow is commonly based on the porphyritic character of its upper portion and on its position immediately above the Wolverine sandstone. With these aids it can be recognized more easily and certainly than most of the other flows.

     What is classed as the Kearsarge flow does not everywhere consist of a single flow; in many place there are two or more flows at the Kearsarge horizon that contain feldspar phenocrysts and are grouped as Kearsarge. In the principal productive area, from the Centennial mine to the Gratiot mine, the amygdaloid of the lowest flow of the series has been mined, and only locally have the amygdaloids of the "west lodes" been shown to contain copper in paying quantity. In this area the higher flows are relatively thin, phenocrysts are few, and the amygdaloidal tops are of the cellular type and usually but little oxidized.

THICKNESS

     Seneca No. 1 shaft: Diamond-drill hole No. 6, more than 127 feet in five flows; basal trap 63 feet. Diamond-drill hole No. 3, 74 feet from top cut, five amygdaloids and base of series not reached. Diamond-drill hole No. 1, basal trap more than 84 feet, sandstone not reached. Diamond-drill hole No. 5, 950 feet north of No. 1 shaft, 113 feet of Kearsarge flows with four amygdaloids, basal trap 24 feet. The old Seneca No. 1 shaft is sunk near the Wolverine sandstone, and crosscuts were extended from it into the hanging wall. First level, crosscut 150 feet; second level, crosscut 50 feet, drift on an amygdaloid; third level, crosscut about 350 feet, apparently cutting the entire series of Kearsarge flows, drift about 700 feet, apparently on top amygdaloid; fifth level, crosscut about 230 feet, drift on an amygdaloid, possibly the top amygdaloid.

     Ojibway: Kearsarge apparently consists of two or more flows. Basal flow at No. 1 shaft reported 35 to 85 feet, at No. 2 shaft 260 to 360 feet.

     Cliff: Diamond-drill hole No. 1 at shaft, Wolverine sandstone 33 feet, trap 93 feet, amygdaloid 6 feet, trap 28 feet, amygdaloid 7 feet (west lode?). Diamond-drill hole No. 11, 1,900 feet along strike from south boundary, Wolverine sandstone 2 feet, basal trap 107 feet, amygdaloid 22 feet, second trap 7 feet, second amygdaloid 10 feet, followed by a series of small flows. Diamond-drill hole No. 12, Wolverine sandstone 3 feet, basal trap 46 feet, amygdaloid 5 feet, second trap 12 feet, amygdaloid (Kearsarge) 14 feet, third trap 7 feet, amygdaloid (Kearsarge) 8 feet. Diamond-drill hole No. 3, 5,200 feet north of south boundary, Wolverine sandstone 19 feet, basal trap 174 feet, amygdaloid (Kearsarge) 24 feet, second trap 81 feet, amygdaloid 11 feet. Diamond-drill hole No. 4, 5,600 feet north of south boundary, Wolverine sandstone 5 feet, basal trap 113 feet, amygdaloid 18 feet, second trap 77 feet, amygdaloid 13 feet.

     Central mine: Kearsarge as scaled from a cross section, 235 feet in three flows. Diamond-drill hole No. 2, Wolverine sandstone thin, basal trap 70 feet, amygdaloid 5 feet, second trap 57 feet, amygdaloid (Kearsarge) 33 feet.

     Mandan: Diamond-drill hole No. 9. Wolverine sandstone thin, basal trap 55 feet, amygdaloid 6 feet; appears to be one flow.

     From the records given above it is apparent that north of the Gratiot mine the basal Kearsarge flow becomes decidedly variable in thickness, ranging from 24 feet in diamond-drill hole No. 5, Seneca, to 260 feet or more in No. 2 Shaft, Ojibway, 19 feet in the Frontenac, and 27 and 45 feet at Mandan. In contrast with. the main productive area, the basal flow is in most places thin, and the whole series does not maintain the thickness of the basal flow in the area from the Gratiot to the Centennial mine.

The following observations were made south of the productive area:

     Laurium: Diamond-drill hole No. 3, 1,700 feet south of north boundary, Wolverine sandstone 10 inches, basal trap 110 feet, amygdaloid 10 feet, second trap 4 feet, amygdaloid 2 feet. Diamond-drill hole No. 2, 800 feet north of shaft, Wolverine sandstone 3 feet, basal trap 141 feet, amygdaloid 8½ feet. Diamond-drill hole No. 4, 900 feet from extreme south boundary, Wolverine sandstone 10 feet, basal trap 144 feet, amygdaloid 11 feet, second trap 4 feet, amygdaloid 7 feet.

    Calumet & Hecla: Eighty-first level crosscut, Red Jacket shaft, two small flows over the main Kearsarge lode; basal flow 181 feet. 

     La Salle: Diamond-drill hole No. 12, opposite No. 2 shaft, Wolverine sandstone 2 feet, basal trap 131 feet, Kearsarge amygdaloid 9 feet, trap 75 feet. No. 2 La Salle shaft is on first amygdaloid. Diamond-drill hole No. 13, 1,700 feet south of No. 2 shaft, from top down, hanging-wall trap 60 feet, top Kearsarge amygdaloid 4 feet, trap 15 feet, amygdaloid 4 feet, trap 20 feet, amygdaloid 14 feet, trap 20+ feet, Wolverine sandstone not noted. Diamond-drill hole No. 14, 250 feet down dip from No. 13, hanging-wall trap 65 feet, Kearsarge amygdaloid 4 feet, Kearsarge trap 33+ feet. Diamond-drill hole No. 1, 5,200 feet south of No. 2 shaft, at No. 5 La Salle, Wolverine sandstone 7 feet, basal trap 28 feet, amygdaloid 4 feet, second trap 28 feet, amygdaloid 6 feet, third trap 10 feet, amygdaloid 12 feet, fourth trap 29 feet, amygdaloid 1½ feet, fifth trap 2½ feet, amygdaloid 6 inches, sixth Kearsarge trap 4½ feet, amygdaloid 7 feet. Diamond-drill hole No. 4, at No. 6 La Salle, Wolverine sandstone, first flow, lowest Kearsarge trap 42 feet, amygdaloid 3 feet; second flow, trap 8 feet, amygdaloid 7 feet; third flow, trap 14 feet, amygdaloid 4 feet; fourth Kearsarge trap 14 feet, amygdaloid 7 feet; hanging-wall trap 14 feet. Diamond-drill holes Nos. 6, 9, 10, 1,500 feet south of No. 6 La Salle; diamond-drill hole No. 9, Wolverine sandstone 1 foot, basal trap 96 feet, amygdaloid 2 feet, second trap 37 feet, amygdaloid 4 feet, hanging-wall trap 62 feet.

     Franklin Jr. new shaft: First Kearsarge amygdaloid 7 feet, trap 28 feet; second Kearsarge amygdaloid 6 feet, trap 33 feet; third Kearsarge amygdaloid 9 feet, trap 2 feet; Wolverine sandstone(?) 4 inches.

     Arcadian No. 1: Total flow 109 feet; No. 2, total flow 101 feet.

     Naumkeag: Diamond-drill hole J, Wolverine sandstone 1 foot, trap 57 feet, amygdaloid 17 feet.

     Isle Royale mine: Wolverine sandstone 1 foot, trap 49 feet, amygdaloid 5 feet.

     Atlantic: Wolverine sandstone 6 feet, trap 40 feet, amygdaloid 17 feet.

     From these observations it is apparent that south of the Centenial mine there is a thinning of the Kearsarge flows, and that south of Nos. 1 and 2 La Salle the basal flow is thin and  the series generally consists of a succession of thin flows.

CHARACTER THE KERSARGE AMYGDALOIDAL 

     GENERAL FEATURES

     Next to the Pewabic, the Kearsarge lode is the most regular of the large productive lodes of the district, yet it varies notably in character from place to place. In the main productive area the amygdaloid can be roughly separated into material of three types - namely , "fragmental lode," banded amygdaloid, and "foot lode."

     The "fragmental lode" consists of irregular angular to subangular fragments of amygdaloid. The amygdaloid fragments are predominantly fine and contain very numerous but small amygdules, indicating relatively rapid solidification; but mixed with the fine fragments are some of coarser texture.

     In the Kearsarge lode as a whole individual fragments rather rarely exceed a foot in greatest dimension, and most of the fragments range from 6 inches to a fraction of an inch. In the top portion the fragments average smaller than toward the base. In position "fragmental lode," if present, is always at the top, immediately beneath the hanging-wall trap. It gives place downward either to cellular banded amygdaloid or to "foot lode;" if the former, the transition is likely to be gradual; if the latter, it is more likely to be abrupt.

     The thickness of the "fragmental lode" probably averages 5 to 6 feet but ranges from 20 feet down to the vanishing point. Very commonly, where the "fragmental lode" is thickest it bulges into the hanging wall, indicating that it formed slight elevations on the surface that was buried by the overlying flow, and it also extends deeper into the underlying material at such places.

     The banded amygdaloid, as contrasted with the "fragmental lode," is an unbroken rock body over considerable areas. The amygdules are commonly more abundant at certain horizons, giving the rock a banded appearance in cross section. In texture it varies with distance from the surface of the lode. Where it forms the top of the lode the upper portion is fine textured and it increases in coarseness with increase in distance from the surface. Where it is covered by "fragmental lode" the finer-textured part is not present. Evidently the "fragmental lode" offered the same protection from rapid cooling as the chilled upper portion of the banded amygdaloid.

     The banded amygdaloid may lie immediately below the hanging-wall trap or it may grade upward into "fragmental lode." Downward it grades into "foot lode." In most places it is less than 6 feet thick, but it may exceed that thickness locally, as in some parts of the upper levels of the Wolverine, North Kearsarge, Mohawk, and other mines.

     The rock in the zone between the banded amygdaloid and the footwall trap is called "foot lode." It  differs from the banded amygdaloid in having a coarser texture, larger and fewer amygdules and less tendency for the amygdules to form in bands. It grades upward into cellular amygdaloid or underlies "fragmental lode.'" in a very few places it immediately underlies the hanging-wall trap. Downward it grades into the footwall trap. Locally it contains a few fragments of cellular amygdaloid. It rarely exceeds 6 feet in thickness.

     From the foregoing statements it is apparent that, the lode may consist of "fragmental lode," banded amygdaloid, and "foot lode"; of "fragmental lode" and "foot lode"; of banded amygdaloid and "foot lode"; or rarely of "foot lode" alone. The thickest parts of the lode always comprise a fragmental layer and in many places all three types. The thin parts probably consist most commonly of banded amygdaloid and "foot lode," though a lava-cemented fragmental thin lode is a common type.

     The average thickness of ground stoped varies somewhat in the different mines of the Kearsarge lode. In several of the mines the lode has been so largely removed from the part developed that it is possible to estimate roughly the average thickness stoped from the quantity of rock produced and the area mined. Such estimates are shown on page 199.

     The amount of ground left in stoping differs considerably in different mimes; it probably ranges from 10 to 35 per cent. The South Kearsarge has one of the highest recoveries, and its greater stoping width as calculated is probably due in part to that fact. For the Mohawk the actual stoping width is said to be about 12 feet, whereas the calculated width is 9.5 feet, indicating that about 20 per cent of the lode is left.

     It appears from the calculations that the average thickness of lode stoped decreases from the South Kearsarge northward. That this difference can mot be attributed to sloping wider than is warranted in the South Kearsarge and part of the Wolverine is indicated by the average high yield in copper per ton of rock from these mines. It must of course be recognized that there is a decided variation in the thickness of lode in different parts of individual mines. In the Mohawk, for example, the lode averages distinctly thicker at the south than at the north end.

     The largest area of thin and cellular amygdaloid in the productive part of the Kearsarge lode extends along the outcrop from about the north boundary of the, South Kearsarge to the Mohawk mine. For much of the distance it extends but a few hundred feet below the outcrop, but in the North Kearsarge and Wolverine mines it reaches as deep as the twentieth level. (See pl. 40.)

     Another large body of cellular rock is present in the north end of the Mohawk mine. At the surface it extends from about No. 4 shaft to the north boundary, and in the bottom levels from about No. 2 shaft to the boundary. Interspersed with fragmental rock the lode rock of this type apparently extends beyond No. 1 Gratiot shaft, though the lode in that area has been less developed. It is also predominant north of the new Seneca shaft in the deeper levels. Fragmental lode rock occurs along the Mohawk-Gratiot boundary in the upper levels of No. 2 Gratiot, and smaller areas in the upper and intermediate levels of No. 1 Gratiot and in the lower levels of the new Seneca shaft. A third body of cellular lode is found in the lower levels north and south of Allouez No. 1 shaft, and a smaller body is present north of No. 2 Allouez. Another stretch of thin lode is present in the North Ahmeek, extending from No. 4 shaft northward along the Mohawk boundary beyond No. 4 Mohawk. The bodies of thin lode included in the general area of thick lode thus far outlined have their greatest extent along the strike of the lode and relatively small extent on the dip. If this pattern proves to be typical, it may be possible to get some idea of the distance through a thin bar from its extent along the strike.

     LOCAL OBSERVATIONS

     At Ojibway, according to Hubbard,⁶ there is an east lode and a west lode that are copper bearing. Both seem to be irregular in thickness and to be cut out in places. Hubbard suggests that the lode has been eroded and that the old stream channels are recognizable. According to his description the lode is present in the channels and absent from the bounding ridges. To account for this Hubbard⁷ suggests that after the erosion of valleys they were partly filled with rock material, which was later covered by the flow. Apparently there are two rather persistent copper-bearing lodes separated by trap. The report for 1909 states that at No. 1 shaft, "the east lode is from 24 feet in width on the 500-foot, level to 17 feet on the 650-foot level and contains copper on both levels. The west lode was reached by crosscutting through 17 feet of trap rock. The west lode is about 17 feet wide, horizontally on both levels and contains copper." 

     Little information is available as to the character o f the lode at the Cliff shaft. From an inspection of the dump the impression was gained that the lode  is mainly of the cellular type, though some breccia is present. The diamond-drill hole at the shaft shows two flows, the bottom one 134 feet thick, with a 6-foot amygdaloid, and the top one 30 feet thick, with a 7-foot amygdaloid. In the main the lode seemed rather poorly oxidized. Feldspar phenocrysts are present but rather sparingly. Most of the work was done on the lower amygdaloid, from which most of the material on the dump was probably derived.

     At the Rhode Island mine 10 feet of breccia lode, almost a "conglomerate," was noted by Lane. The thickness of the basal bed is 19 feet; the west flow is 86 feet thick, with 11 feet of red amygdaloid.

     At the Franklin Jr. mine the Kearsarge amygdaloid was located,⁸ and the cores show a little copper.⁹ The thirty-second level crosscut showed enough copper on the footwall side of the lode to warrant further exploration, according to the report of the company. The explorations in the new Kearsarge shaft show three Kearsarge flows with cellular tops.

     In the Delaware drill section the Kearsarge amygdaloid has been cut in several diamond-drill holes. In all it is a thin (3 to 4 feet), nonfragmental, poorly oxidized amygdaloid. Some of the holes cut "west" lodes also with thin, nonfragmental, poorly oxidized amygdaloids.

     South of the main productive area the lode, so far as known, seems to be thinner and less fragmental than in the productive area. This change is apparent in the south end of the Centennial mine. Little is known of the character of the lode in the Calumet & Hecla, but farther south, in the La Salle mine, it is only locally fragmental and in general only moderately oxidized. The diamond-drill records show that the Kearsarge flow in La Salle ground consisted of three to five thin flows with amygdaloids. In the south shafts the development seems to have been on the upper amygdaloid of this series. The north shafts are evidently on the first amygdaloid above the Wolverine sandstone. In the Laurium ground the diamond-drill record indicates but one thick flow.

     In the productive area of the Kearsarge lode the copper has practically all come from the first amygdaloid above the Wolverine sandstone.

     From these notes it appears that nowhere outside of the main productive area have large areas of thick "fragmental lode" been discovered.

     STRUCTURE

     ALLOUEZ ANTICLINE

     The major structural feature of the productive part of the lode is the Allouez anticline. The axis of this arch passes near No. 1 Ahmeek shaft; the beds flatten out at the south near the Centennial  shafts and at the north between Nos. 3 and 4 Mohawk Within these limits the average divergence from a plane in the position of the Kearsarge bed outside this fold is about 5° for both limbs, or about 9 feet in 100 feet. The steepest dips are at the crest of the anticline, and if the dips continue down the lode at the same angle as at the surface, the anticline must gradually flatten, and at 10,000 feet down the dip it must nearly disappear. The anticline is much less pronounced in the higher beds of the series than it is toward the base. 

FAULTS AND FISSURES

      By far the most prominent series of fissures strike a little west of north and as a rule dip steeply eastward. Among these are the shatter zone, the Mohawkite, Mass, and Fulton fissures, and half a dozen fissures in the Mohawk mine. Fissures of this series are less abundant to the south but are present throughout the developed area.

     The shatter zone that passes along the boundary between the North Ahmeek and Mohawk mines offsets the lode in the upper workings of the Mohawk, but this offset decreases with depth till in the North Ahmeek it is little more than the width of the lode. This shatter zone is narrower than the Ahmeek-Allouez zone but resembles it closely in other respects. It is considerably wider in the Mohawk than in the North Ahmeek. The fault south of No. 1 Gratiot offsets the lode about 50 feet to the west on the north side.

     The other prominent fissures commonly show a little gouge, and in places there is some brecciation of the adjacent rock.. Not uncommonly the fissure zone widens out to 2 to 3 feet.

      Another set of fissures strikes approximately east, or nearly at right angles to the north-south fissures, and usually dip steeply south. None of these are prominent, and few can be traced for more than a few hundred feet. There are numerous fissures in the mines that do not seem to fall into any well-developed regional system, but they are commonly small and traceable for only short distances.

ALTERATION AND MINERALIZATION

OXIDATION

     Oxidation was the earliest alteration of the lode. The oxidation of the Kearsarge and other lodes is fully discussed in the general section of the report (p. 34). The fragmental portions of the Kearsarge lode are highly oxidized and unusually high in ferric oxide. The oxidation is believed to have taken place during the cooling of the lava, earlier than and quite independently of the deposition of copper.

ALTERATION ACCOMPANYING MINERALIZATION

     The alteration that took place subsequent to the oxidation may not all have occurred at the same time, but to separate it clearly is not easy. Much of it seems to have been closely associated with the deposition of copper, but certain phases of the alteration seem to have been more widespread than the copper deposition and not necessarily closely tied to it. For example, red feldspar, though present nearly everywhere in the Kearsarge lode, is distinctly variable in amount. In La Salle North Kearsarge, North Ahmeek, and Mohawk ground it is rather abundant, but in South Ahmeek ground there is less. Epidote is also far more widely distributed in the lode than important copper deposits. It may be added that what is true of the Kearsarge lode is also true of other lodes. Some that have very little copper show a more or less pronounced epidotization. This suggests that some of the changes may not have been due primarily to the copper-bearing solutions but probably to the general temperature conditions that accompanied the mineralization.

     The mineralization that followed the oxidation of the lode bore a distinct relation to the compositions of the lode after oxidation. Thus epidote, a ferric silicate, is abundant in the more highly oxidized portion of the lode but is much less abundant in the "foot lode" that was less highly oxidized. Chlorite and pumpellyite, ferrous-ferric silicates, are characteristic of the less oxidized "foot lode" and also of the basal amygdaloid of the hangingwall trap, though they are also present in the more highly oxidized portion of the lode.

     The change from epidote to chlorite in passing from the Kearsarge lode to the basal amygdaloid of the overlying trap is very sharp. Areas of these rocks but a fraction of an inch apart show the characteristic mineralization of each. In the west lodes, which are much less oxidized than the main lode, pumpellyite is relatively abundant. Minerals that do not contain iron show no such control as indicated above. Thus, quartz and feldspar are distributed throughout the lode, and so is laumontite where present; in fact, so far as recognized, the control is confined to the iron minerals.

YIELD

      In general, the Kearsarge lode is richest near the hanging wall; the richest ore is not always, perhaps not usually, at the very top, but the first 3 to 5 feet is the richest part of the lode and grades downward into leaner rock. In the Wolverine mine the "foot lode" was not extensively mined in the earlier years, but it is said to have been in the last few years a rather large factor in the production. In the earlier years the rock mined averaged 25 to 30 pounds to the ton; in the last few years it has averaged 15 to 16 pounds, indicating that the "foot lode" is much lower in copper than the upper part, though some low-grade material from the top part has been mined at the same time. A similar but much less marked change occurred in the South Kearsarge when the "foot lode" began to be more extensively mined.

     The copper derived from a given area of lode varies to a considerable extent with the thickness of the lode, though there are notable exceptions. For the larger mines on the Kearsarge as to which data are available, the following table shows the average calculated thickness of lode stoped, the average quantity of rock  mined per square foot of lode area, and the average yield of copper.

Rock mined and copper produced per square foot of Kearsarge lode

     The relatively large amount of unprofitable ground in the Wolverine, Centennial, and North Kearsarge make the figures for these mines less accurate.

      There is a rather regular decrease in the average stoping width from, the South Kearsarge mine northward to the. Mohawk, the average in the latter mine being fully 3 feet less than that in the former. Except in the South Ahmeek (Nos. 1 and 2; there is also a decrease in the copper per square foot of lode. The Wolverine has the highest-grade rock, and in part of the mine the lode is as thick as in the South Kearsarge, so that this part probably has the highest yield per square foot of lode. The grade of rock in the Ahmeek has averaged distinctly higher than that in the South Kearsarge, but the average thickness stoped is 2 feet less, so that the average per square foot of lode is slightly less.

      It appears that although the lode is mineralized from the Centennial to the Mohawk, two areas richer than the average have been developed. One includes the South Kearsarge and Wolverine with adjacent parts of the Centennial and North Kearsarge; the other includes the South Ahmeek, South Mohawk, and parts of the Allouez. There are also certain poor areas that in general correspond to the areas of thin and cellular lode already outlined and associated with the strong fissures and fissure zones. (See pl. 40.)

PROBABLE CAUSES OF RICH AND POOR GROUND

     Three principal causes seem to have been operative in determining the richness of the ground-character of rock, structural relations, and relation to strong fissures. Of these the character of rock and relation to strong fissures are the more conspicuous.

CHARACTER OF ROCK

     Within the productive portion of the Kearsarge lode the thin parts of the lode and those consisting of dense, trappy amygdaloid are consistently poor. In the larger areas where the lode is poor it is thin or tight and relatively impermeable. The richest ore has been formed in thick masses of strongly developed fragmental top. The thick parts of the lode are not all rich, nor are parts of apparently equal thickness similarly rich, but rich parts of the lode are always thick or loose and fragmental in texture. Outside of the main productive area there are, so far as available data indicate, no large areas of thick fragmental top, most of the outside exploration having disclosed only thin or cellular amygdaloid.

EFFECT OF DEPTH ON THE COPPER CONTENT OF THE LODE

      The study of the Kearsarge lode has shown no evidence of leaching of copper near the surface and reprecipitation at greater depth. Where the lode is poor at the. surface, as in parts of the Wolverine and North Kearsarge mines, the rock is impervious and unfavorable, and there is no indication that it was ever well mineralized. Where similar rock is encountered in the deeper workings, as in the lower part of the Allouez and in part of the North Ahmeek, the low copper content is encountered.

      If the mineralizing solutions in the main were traveling up the lode, the lode in general must continue permeable down to the connection with the source of the solutions, otherwise they would not have found their way to the level now developed. That mining will disclose areas of unfavorable rock and variation in the copper content at greater depth is to be expected from the known conditions in the developed areas. The encountering of an area of unfavorable rock should not be regarded as discouraging for the lode as a whole, though it may be so for an individual property. Poor ground, due both to character of rock and to the influence of fissures, is likely to be found here and there at greater depth as it has been to the present depth.

     It is not intended to imply that a general decrease in the copper content of the Kearsarge lode will not be found at depth, but there is no reason to think that it will be other than a gradual falling off for the lode as a whole. So far as known, the causes that resulted in a decrease in the grade of the rock on the Calumet & Hecla conglomerate lode - namely, an increase in the thickness and extent of the lode with increased depth - will probably not affect the Kearsarge lode. The conditions are more likely to approach those of the Quincy lode, where a depth nearly as great as on the Calumet & Hecla conglomerate has been attained with no notable decrease in copper content.

MAYFLOWER-OLD COLONY MINE

STRUCTURE

     The earlier development of the Old Colony or southern portion of the property consisted of several shafts and a tunnel. The Old Colony tunnel starts near the Keweenaw fault and was driven across the series a distance of about 2,500 feet, or to the fourth flow above the "Big" trap. The No. 1 and No. 2 shafts were on amygdaloids about midway between the Kearsarge amygdaloid and the "Big" trap. No. 2 was on a bed a little higher in the series than No. 1.

      About 1910 an extensive drilling campaign was undertaken by both the Mayflower and Old Colony companies to prospect the lower portion of the copper bearing series on their properties. After this tract had been more intensively drilled than any other area in the Copper Range, the two companies were merged, and the present No. 1 shaft was sunk to a depth of 1,760 feet to prospect the Mayflower lode. The shaft starts in the "Big" trap, but the prospecting has been in the rocks below the Mayflower fault, on the 1,450 and 1,700 foot levels. The Mayflower amygdaloid occurs above two well-defined conglomerates, which have been a great help in working out the structure of this much-faulted block of ground. At the end of 1924 a crosscut was being run N. 70° W from the seventeenth level, No. 1 shaft, to prospect above the "Big" trap at the horizon of the "St. Louis" amygdaloid.

    6 Ojibway Mining Co., Repts., 1909-1912,

    7 Lake Superior: Mining Inst Proc. vol. 17, p. 234, 1912.

     8 Franklin Mining Co. Rept. for 1905, p.12.

     9 Idem for 1916, p8.

     10 Marvine, A. R. Michigan Geol. Survey, vo1. 1, pt. 2, p. 61, 1873.

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