The Sunset Copper Mine was considered to have been the biggest mining operation in the Index District of Snohomish County, Washington, United Stated. This whole entire mining operation was rather reported to have been located on Trout Creek that was located by the north fork of the Skykomish River System. Almost all transportion into this property was reached from Index by a surface tram road, which was six miles in length, and built along the south side of the river. Other statements had stated that this property was first staked by the historical Sunset Mining Company, and consists of thirty-six claims. For the most part the company reported that the first discovery in the area was made on the Sunset Lode Claim, and the Black Bear Claim on June, 19, 1897. Much of the property at the time was first additionally discovered by a prospector known as Arthur C. Egbert. He had then incorporated his own mining company which became known as the Sunset Mining Company on July, 18 1897. Other statements stated that Mr. Arthur C. Egbert had also done this with the assistance of Ezra M. Egbert who became the president. As the company became organize Arthur would also hire on John McManus as secretary, and Nicholas Rudebeck as General Manager. With the company formed it was also reported that the deed was officially filed on August, 2, 1897. Company officials at the time had also issued 1,000,000 shares of stock at a $1.00 a piece within this time period.
1898 - Sunset Mining Company
As this discovery became uncovered it was stated that a fume pipe was installed from the main camp to about half a mile up the creek. From here the water was directly taken from Trout Creek where it was carried to the company's newly developed power house. The water supply within this time period was mainly used to operate all the machinery that provided lighting to the mine and buildings. Other development procedures had also taken place when the company had driven a small adit within the hill on the Star Claim. For the most part the company was mainly aiming to extend this adit into the Brown Bear claim. Almost all development within the adit area had resulted in expanding a crosscut for a distance of 300 feet at the time.
1899 - Sunset Mining Company
Company officials from the Sunset Mining Company would additionally continue to expand the adit workings. All development within this time period had continued to expand th3 adit workings even more when the drift was extended for another 300 feet. It was at this point when the company notice that the vein had travelled northwest, and southeast. As this became encountered a small amount of drifting was done on both directions of the main vein area. In addition to this the company had completed a total of 50 feet of drifting to the northwest, and 20 feet to the southeast. A small amount of ore at the time was being hauled away by the newly establish tramway.
1900 - Sunset Mining Company
As development continued to take place the company, and its workforce continued to expand the drift in both directions. The former is known for traveling a distance of 250 feet, while the latter is 350 feet in length. With development continuing to take place the company would also extract a large amount of ore from the underground workings that year. Nothing else had occurred during that time period of operating the Sunset Copper Mine project.
1901 - Sunset Mining Company
Even more expanding had escalated when the company continued to develop the northwest and southeast drift sections. By this time the former had expanded for a distance of 500 feet, while the latter had its own length of 750 feet on the vein zone. At about 450 feet from the intersection of the crosscut in the right hand drift the company had establish an upraise that was driven for distance of 80 feet on the vein. Even more ore was now being taken out from the underground workings that year.
1902 - Sunset Mining Company
The main tunnel at the time was even going through more expansions when it was driven further into the underground workings. Now with the mine expanding the main tunnel area was reaching its own total length of 1,075 feet. This major development procedures resulted in constructing short drift sections to the right and left of the workings. A small amount of development was also being focus on developing a second tunnel into the hill side of the Black Bear Claim. Much of this development phase had only driven the upper tunnel workings for a distance of 40 feet. Nevertheless, this main tunnel system had also been driven on the upper part of the hill from the lower adit workings.
1903 - Sunset Mining Company
For the most part the company had focus on developing the upper adit workings when the tunnel had a total length of 250 feet, In addition to this development the company was able to intersect the same vein system as the lower adit workings previously worked on. With this discovery made the company would continue to expand the workings when drifts were driven to the right and left at unknown distances, A huge amount of ore was also reported to have been stoped out in the left hand drift as a raise was driven to the surface. As the ore came from the mine it was than carried by tramway to Index where it became shipped to the Tascoma Smelter. Besides the upper, and lower adit workings the company also commence development of another tunnel on the ravine claims. For the most part almost all the underground workings are considered to be mainly developed in granodiorite. In many case the rock on the eastern side of this property is considered to come in contact with quartzite, and intrusive rocks. Much of the vein systems within this property are also considered to have strike trends of north 78 degrees west with a pitch of 90 degrees to the east. The vein within the stope sections of the tunnel were considered to also have a width of 40 feet with the west wall still not determined. Other statements had stated that the ore-body become more narrow towards the surface, and as well as in depth.
For the most part the quartz vein in the lower tunel is known to average a width between 2 to 16 feet, and the vein it self is considered to pitch out, In many cases this leaves the vein in a zone that's known to comprise of granodiorite with little quartz, and a very fin seam of ore. In several case the ore-body is strongly determined to appear in lens with its long axis entirely lying in the plane of the fissure, More so this formation also represents that portion of the fissure which is much wider than the average, and the mineral solution is strongly determined as the cause of depositing these large parts of the ore-bearing minerals. The whole entire formation that forms this ore body mainly consists of chalcopyrite, a small amount of bornite, with pyrite, and marcasite in a gangue composed of quartz, calcite, and large altered granodiorite.