The Green Horn occurrence is located at 1768 metres elevation on the north side of Carpenter Crook valley about 4 kilometres above Cody. The occurrence lies on the boundary between Reverted Crown grant Lots 1306 and 2055. Most of the underground workings are on the Home Rule Reverted Crown grant (Lot 2055).

The Home Rule claim was staked in 1895 and the Greenhorn about 1893. Workings comprise several adits and opencuts over a vertical range of about 243.8 metres, and are chiefly on the Home Rule claim.

According to Cairnes (1935), "Work done to 1925 on this property has been mainly prospecting and has, on the whole, provided encouragement for further exploration". Since 1925 the only work recorded was in 1949, following the acquisition of the claims by John R. Kenney. Development at that time consisted of collaring an adit on the Little Jack claim with the object of locating a possible downward extension of a vein indicated in the Greenhorn tunnel 140 metres above. The tunnel was still in overburden when work stopped in August.

Regionally, the area lies on the western margin of the Kootenay Arc, in allochthonous rocks of the Quesnel Terrane. In the vicinity of the occurrence, the Quesnel Terrane is dominated by the Upper Triassic Slocan Group, a thick sequence of deformed and metamorphosed shale, argillite, siltstone, quartzite and minor limestone. Rocks of the Slocan Group are tightly and disharmonically folded. Early minor folds are tight to isoclinal with moderate east plunging, southeast inclined axial planes and younger folds are open, southwest plunging with subhorizontal axial planes. The sedimentary sequence has been regionally metamorphosed to lower greenschist facies.

South of the occurrence, the Slocan Group has been intruded by the Middle Jurassic Nelson intrusions which comprise at least six texturally and compositionally distinct phases ranging from diorite to lamprophyre. The most dominant phase is a medium to coarse grained potassium feldspar porphyritic granite. Several feldspar porphyritic granodiorite dikes, apparently related to the Nelson intrusions, also cut the sedimentary sequence near the occurrence (Paper 1989-5).

The Green Horn and Home Rule Reverted Crown grants are underlain by quartzite, calcareous argillite and slate of the Slocan Group. The strata are folded in a northwest-trending syncline with limbs dipping at low angles to the north and south. The occurrence consists of two or more well-defined fissure veins striking 080 degrees and dipping steeply to the south. The main vein is 25 centimetres wide and consists mostly of fragments of galena enclosed in quartz which cements blocks of wallrock. Small pockets of more massive galena also occur along the vein. Siderite, pyrite and chalcopyrite occur in minor amounts with the galena. The vein has been explored in at least two adits on the Home Rule claim and several trenches on the Green Horn property.

Production in 1915 and again in 1965 yielded 10,544 grams of silver, 31 grams of gold, 2329 kilograms of lead and 1076 kilograms of zinc from a total of 14 tonnes mined.