The type section of the "Diamond Peak Quartzite" was designated on the slopes of Diamond Peak in the Diamond Range by Hague (1883). The type section was measured and described by Brew (1961) who noted numerous high-angle faults, at least one major thrust, and the absence of part of the Diamond Peak Formation at that locality.

The Diamond Peak Formation is Upper Mississippian (upper Meramecian to Chesterian) in age. The Tonka Formation of Dott (1955) is equivalent to the Diamond Peak in the Elko area. The sandy eastern facies of the Diamond Peak in southern White Pine and northern Nye and Lincoln Counties has been designated either the Scotty Wash Quartzite (Kellogg, 1960), named for exposures in the Fairview Range in Lincoln County by Westgate and Knopf (1932), or the informal Illipah Sandstone (Christiansen, 1951; Douglass, 1960). This eastern facies is generally finer grained, better sorted and more quartz-rich than western and northern exposures of the Diamond Peak Formation.

The reader should be aware of the gradational nature between the Chainman and Diamond Peak Formations which essentially represent facies within one major depositional sequence. The terms assigned to these rocks are somewhat inconsistent on a regional basis so that locally, one mappers' Diamond Peak would be anothers Chainman Formation or undifferentiated Chainman and Diamond Peak Formations. Many of these inconsistencies have been removed, but some still exist. Where mapped as Chainman and Diamond Peak Formations, the unit is described under the most appropriate designation representing the dominant formation.

In the Diamond Mountains the Diamond Peak Formation conformably and gradationally overlies the Chainman Formation and is conformably and gradationally overlain by the Ely Limestone. Brew (1961a) reports that at its type section the formation is composed of 45 percent siltstone, 20 percent sandstone and silicified sandstone, 12 percent conglomerate, 6.5 percent limestone and 5.5 percent limestone-cobble conglomerate.

The distinctive Diamond Peak conglomerates are composed of angular to rounded pebbles, cobbles and boulders of chert, quartzite and lesser amounts of limestone. Green, grey, black and white chert clasts and grey and green quartzite fragments were eroded from the Vinini and Valmy Formations. Rapid lateral facies variation between coarse conglomerate and fossiliferous limestones are not uncommon in the Diamond Peak (Nolan and others, 1956).

In the Diamond Mountains, Brew (1961a) broke the Diamond Peak into the following informal mappable units in ascending order: Unit A is 280 feet of interstratified, thick-bedded grey-weathering chert, quartzite, conglomerate, limestone-pebble and cobble conglomerate, claystone, siltstone, and thin-bedded grey, fine to medium-grained silicified sandstone; Unit B is 1,270 feet of interbedded thin-bedded siltstone and silicified sandstone, claystone, and minor lenticular conglomerate; Unit C is 240 feet of thick-bedded grey to brown-grey chert and quartzite-pebble and cobble conglomerate and overlying siltsone, claystone, sandstone and thin-bedded grey limestone beds; Unit D is 380 feet of thick-bedded grey and blue-grey limestone interbedded with calcareous brown sandstone, grey claystone and siltstone, grey brown chert and quartzite pebble and cobble conglomerate, and intraformational limestone conglomerates with limestone phenoplasts up to 10.1 cm in diameter; Unit E is 570 feet of limestone, sandstone, siltstone, conglomerate, claystone, and limestone conglomerate; Unit F is 315 feet of purple and green siltstone and claystone, green sandstone, green chert-cobble conglomerate, and green, purple and grey limestone conglomerate; Unit G is 250 feet of thick-bedded and dark chert-pebble and cobble conglomerate and minor siltstone, silicified sandstone, and limestone conglomerate overlain by poorly exposed siltstone; and the uppermost Unit H is 220 feet of thin to thick bedded blue-grey limestones characteristic of the overlying Ely Limestone with alternating silicified sandstone, siltstone and limestone conglomerate.

In the southern Adobe Range, Sillitonga (1974) divided over 8,000 feet of the Diamond Peak Formation into 6 members complicated by low-angle faulting, A through F. Member A roughly correlates to units B through D of Brew (1961a). Members C and D are roughly equivalent to unit E, and Member F is the uppermost unit. Member A, the lowest member, is about 6,600 feet of massive conglomerate in beds up to 30 feet thick, interbedded with thin thick-bedded conglomerates in 4 inch to 3 foot thick beds. The conglomerates are gray to brown and contain pebbles of rounded to subrounded, gray quartzite, and subangular to subrounded gray, green and reddish-brown chert and light gray sandstone from 0.5 to 2.5 inches in diameter. Locally cobbles 10 to 15 inches in diameter are present. No grading or imbrication were observed in the conglomerate which often grades into conglomeratic coarse-grained, subrounded to rounded sandstone, siltstone and shale which are commonly laminated, cross-laminated or cross-bedded (Sillitonga, 1974).

Member B is composed of thick-bedded to massive gray and brown quartzite and chert-pebble and cobble conglomerates overlain by gray to olive sandstone and siltstone with 2 inch to 1 foot thick laminations. The sandstones are fine to coarse-grained, subangular to rounded, and poorly to moderately sorted. The sands are composed of 20 to 35 percent quartz, 25 to 35 percent chert, and 20 to 35 percent rock fragments. The 750 foot thick Member B, is believed to be in the same stratigraphic position as Member A.

Member C overlies Member B and is composed of about 400 feet of black and greenish-gray silty and siliceous shale and calcareous shale. Interbedded gray to black limestone lenses up to 1 inch thick and several tens of feet long contain abundant brachiopods, corals, crinoids and bryozoans. Several thin beds of medium-grained, moderately sorted, subangular to rounded sandstone with low porosity are also interbedded.

The basal portion of Member D conformably overlies Member C and is composed of dark blue-gray and gray limestone interbedded with sandy limestone, and laminated and cross-bedded calcareous siltstone, calcareous sandstone and pebbly sandstone. The middle portion of this member is dominantly composed of sandstone with interbedded greenish-gray siltstone, gray and brown cross laminated, fine-grained sandstone, shale, gray oolitic limestone, and gray quartzite and chert-pebble conglomerate. Fossils in this member include brachiopods, crinoids, and abundant corals (Sillitonga, 1974). Member D is about 245 feet thick. Member E is only present in the upper plate of a fault and consists of about 660 feet of gray to yellowish-gray, cross-bedded quartzite and chert pebble and cobble conglomerate interbedded with laminated siltstone, and coarse-grained, slightly porous, silicified and pebbly sandstone.

The uppermost Member F is about 450 feet of brownish-purple and reddish conglomerate which alternates with brownish-purple and reddish cross-bedded, coarse-grained, subangular to rounded sandstone and conglomeratic sandstone. Pebbles and cobbles of chert in Member F are up to 4 inches in diameter (Sillitonga, 1974).

In the Buck Mountain-Bald Mountain area, the Diamond Peak contains abundant coarse cobble and pebble-conglomerates containing green, yellow, grey, and brown quartzite and chert clasts with finer grained gray-green to gray-brown shale and siltstone concentrated mainly in the upper several hundred feet of the formation (Rigby, 1960). This section appears to be transitional between the Diamond Mountains to the north and the Pancake Range to the south.

In the northern Pancake Range, the Diamond Peak Formation is predominantly olive-gray siltstone and silty claystone and interbedded very fine to very-coarse grained sandstone, and about 1 percent quartzite and chert pebble and cobble conglomerate (Stewart, 1962). The rapid southern change in facies from abundant coarse clastics in the Diamond Mountains to finer grained facies with little or no conglomerates in the northern Pancake Range is characteristic of the Diamond Peak and represents a change in clastic supply and proximity to an eroding highland west of the Mississippian Antler foreland basin.

In the central Pancake Range, Mount (1972) described about 950 feet of the Diamond Peak Formation with approximately equal proportions of conglomerate, quartzite and sandstone. Thick beds of brown-weathering, fine to medium-grained orthoquartzite contain oscillation ripples and large-scale cross-bedding as well as land plant fragments in some beds. Less resistant, thin to medium-bedded quartz sandstone with calcareous cement locally contain fragments of brachiopods and corals. The conglomerates are brown-weathering chert and quartzite-pebble and cobble conglomerate which grade laterally and vertically into sandstone (Mount, 1972).

In the southern Pancake and northern White Pine Ranges, the Diamond Peak is composed of thick-bedded medium to coarse-grained, reddish-brown, crossbedded, lithic and quartzose sandstone and fine to coarse-grained chert and quartzite-rich pebble conglomerate with thin interbedded gray sandy limestone and shale in the upper potion of the unit (Gaal, 1958). The sandstones contain abundant land plant fragments.

In the northern Reveille Range, the Diamond Peak Formation is composed of medium to dark-gray or reddish-brown weathering, medium grained laminated to thick-bedded quartzite and conglomerate with subrounded to subangular grains, granules and pebbles of quartzite, chert, and argillite (Ekren and others, 1973).

In the Pinon Range, the Diamond Peak Formation as mapped by Smith and Ketner (1975), includes and supersedes the Tonka Formation of Dott (1955). As defined by Smith and Ketner (1975) conglomerate makes up most of the Diamond Peak in the Pinon Range; commonly 40 to 60 percent of the exposed section. These lenticular conglomerates are commonly massive and in beds 1 to 5 feet thick, and are interbedded with thin, locally crossbedded sandstone layers up to several inches thick. Pebbles and boulders within the conglomerate are commonly chert, quartzite, and sandstone in well sorted to poorly sorted layers. The conglomerates often lens out laterally into tan and yellow shales and siltstones. Many beds are calcareous, and gray locally fossiliferous limestone and calcareous siltstone are often interbedded with the shales. Limestone and calcareous sands are more common in the upper portion of the Diamond Peak (Smith and Ketner, 1975). The Diamond Peak Formation is conformable and apparently gradational with the overlying Moleen or undivided Moleen and Tomera Formations (Smith and Ketner, 1975).

In the Ruby Mountains, Sharp (1942) described an undifferentiated Pennsylvanian unit which Coats (1985) has correlated with the Diamond Peak Formation. It consists of several thousand feet of siliceous chert-quartzite pebble conglomerate, and lesser amounts of gray massive to laminated quartzite, and massive gray-brown to black, chert nodule-bearing argillaceous and oolitic limestone (Millikin, 1978). To the south in the Buck Mountain - Bald Mountain area, the Diamond Peak is composed of interbedded cobble and pebble conglomerate with yellow-gray quartzite, dark-green and yellow-green chert clasts, and interbedded limestone and gray-green, non-calcareous shale and siltstone in the upper 200 feet of the unit (Rigby, 1960).

The Diamond Peak becomes both thinner, finer grained, and chert-poor to the south and east where it has been designated the Scotty Wash Quartzite or Illipah Sandstone by various early workers. The Scotty Wash Quartzite in the Egan Range area is composed primarily of basal sandy shale and siltstone, overlain with rusty weathering, dark-gray, medium-grained and cross-bedded, well-sorted quartzitic sandstone in beds from a few inches to a few feet in thickness, and interbedded olive-gray shale (Langenheim and others, 1960; Kellogg, 1960). The Scotty Wash is about 200 feet thick in the Hamilton District (Steele, 1960).

The Scotty Wash Quartzite has also been retained by Tschanz and Pampeyan (1970) in the Fortification, northern Fairview and Seaman Ranges, and on Dutch John Mountain in northern Lincoln County. On Grassy Mountain and Dutch John Mountain the Scotty Wash is about 75 feet of basal cliff-forming reddish-brown quartzite overlain by about 140 feet of olive-brown to gray shale, interbedded thin limestone beds and yellow to dark-red cross-bedded and rippled shaley sandstone (Tschanz and Pampeyan, 1970). In the Fortification Range it is a grayish-orange to yellowish-brown calcareous sandstone.

The Illipah Sandstone, as described in the southern Butte Mountains, is a sequence composed of a basal buff to reddish-brown quartzitic conglomerate, overlain by interbedded fine to medium-grained, well sorted quartz sandstone, quartzite, and siltstone and shale (Douglass, 1960). Most sections of the Scotty Wash-Illipah interval in the Egan Range-Butte Mountains area are less than 600 feet thick. Sides (1966) dropped the Illipah designation in favor of the Diamond Peak Formation in the central Butte Mountains and reported that on average, the unit is composed of about 40 percent quartzite, 35 to 40 percent interbedded sandstone and limestone, 10 to 15 percent shale, and about 10 percent conglomerate. The fine-grained, rounded to subrounded, well-sorted, green and gray to yellow-gray quartzites are laminated and thickly cross-bedded and are locally calcareous. The conglomerates contain 50 to 60 percent clasts of green, red, brown, white and black chert and quartzite up to 20 mm across. The fissile shales are dark gray to olive. The lenticular limestones are siliceous and silty, thin to medium-bedded, fossiliferous, orange brown to yellow calcarenites and are interbedded with very fine-grained, thinly laminated, graded, rippled, and cross-bedded calcareous brown-gray sandstones (Sides, 1966).

In the Wood Hills and Pequop Range, Thorman (1962) has mapped Diamond Peak in two fault slices where it is composed of chert pebble conglomerate, light gray to brown fine to medium-grained quartzite and siltstone, and lesser fine-grained gray limestone which is concentrated in the upper portion of the unit. Red, green, white and black chert pebbles in the conglomerate are subangular to dominantly well rounded, 1 to 4 inches in diameter and enclosed in a quartzite matrix.

In the Pequop Range, Thorman (1962) divided the Diamond Peak into three members. These are described here in ascending order. The basal member A is about 310 feet of chert pebble conglomerate, siltstone and limestone with a 110 foot thick basal unit of medium-grained light brown quartzite and olive gray conglomerate with chert pebbles commonly 0.5 inches in diameter. The conglomerate is in beds 2 to 8 feet thick and is overlain by about 50 feet of fine-grained, locally laminated limestone, 70 feet of olive-gray faintly laminated siltstone which grades into quartzite. The overlying member B is 435 feet of olive gray to red laminated bryozoan bearing siltstone and gray, locally sandy, fine to medium-grained limestone. The upper member C is 445 feet of interbedded olive-gray, light gray to brown weathering, locally calcareous siltstone and fine-grained, gray, reddish-brown weathering laminated and cross-bedded quartzite in beds a few feet to 40 feet thick. Thin interbeds of conglomerate and calcareous siltstone are present throughout the upper member which is conformably overlain by the Ely Limestone (Thorman, 1962).

To the south, in the southern portion of the Pequop Mountains, Robinson (1961) divided the Diamond Peak into two members. The basal member is 656 feet of fine to medium-grained, pebbly cross-bedded quartzite with angular to subangular chert pebbles, chert pebble conglomerate, and siliceous and micaeous shale and argillite which are found near the top of the member. The upper member is 775 feet of gray fine-grained limestone, siliceous olive-green to black shale, and fine-grained chert pebble conglomerate.

In the Leppy Range, the upper unit of the Undifferentiated Chainman and Diamond Formations is considered equivalent to the Diamond Peak (Schaeffer and Anderson, 1960; Coats, 1985). This member is composed of gray, reddish-brown to gray weathering chert pebble conglomerate. The pebbles are composed of angular to subrounded chert and quartzite from 0.5 to 2 inches in diameter (Schaeffer and Anderson, 1960). The Diamond Peak is gradationally overlain by the Ely Limestone.

In the Pilot Range, the Diamond Peak is composed of medium-gray, coarse-grained quartzite interbedded with gray to yellow-white, orange-brown weathering chert pebble conglomerate which conformably overlies the Chainman Formation and is conformably overlain by the Ely Limestone (O'Neill, 1968). Pebbles in the conglomerate are subangular to subrounded and up to 1.75 inches long.

In the Spruce Mountain Quadrangle, Hope (1972) mapped a sequence of undivided Diamond Peak and Chainman Formations about 2,500 feet thick which overlie the Guilmette along a low-angle fault contact. Most, if not all of this sequence is probably Diamond Peak Formation with removal of the Chainman Formation along the fault. The typical lithology is a chert and quartzite-pebble conglomerate with lesser cross-bedded calcarenite and silicified siltstone, and minor greenish-gray shale with interbedded limestone near the top of the unit (Hope, 1972).

In the HD Range, Riva (1970) mapped a thin fault sliver of Diamond Peak Formation that unconformably overlies western assemblage rocks. The lower 80 feet are composed of conglomerate with black chert fragments while the upper 125 feet are quartzite, and massive argillaceous lenticular beds of pebbly mudstone (Riva, 1970). In the Windermere Hills, the Diamond Peak is composed of a lower unit with black shale and interbedded quartz arenite, and an upper unit of gray or brown, rusty-brown weathering, blocky quartz arenite and rudite and lenticular beds of pebbly mudstone. The arenites typically contain 25 to 20 percent subangular clasts of black, gray, green, and brown chert and rare orthoquartzite and locally contain sole marks such as grooves and prods (Oversby, 1969).

In the Leach Mountains the Diamond Peak is composed of interbedded upward fining, gray and dark reddish-brown, angular to subangular chert-pebble conglomerate which forms about 50 percent of the unit; graded, light gray to brown, fine to medium-grained, laminated and cross-bedded quartzose sandstone with local flute and groove casts which forms about 40 percent of the unit; and about 5 to 10 percent clay-rich reddish-purple quartz siltstone and quartz sand-rich siltstone (LeCompte, 1978). Brachiopods, gastropods, cephalopods, corals, crinoids, poorly preserved land plant fragments, and abundant worm trails are present in the formation.

In the Mountain City Quadrangle in northern Elko County, rocks mapped as undifferentiated Chainman and Diamond Peak Formations are more like Diamond Peak according to Coats (1985). The lithology here is massive, medium-grained dark quartz-chert-rich sandstone to quartzite.

Thicknesses measured in the Diamond Peak are variable and generally thin to the east ranging from about 8,000 feet in the south-central Adobe Range (adjusted from Sillitonga, 1974), 3,525 to 3,750 feet at the type section in the Diamond Mountains (Brew, 1961a), about 4,700 feet in the Carlin-Pinon Range (Smith and Ketner, 1978), 1,800 to 2,200 feet in the Buck Mountain-Bald Mountain area (Rigby, 1960) and 2,500 feet just a few miles to the east in the southern Ruby Mountains (Hose and Blake, 1976), about 4,000 feet near Sherman Creek in the Ruby Mountains (Sharp, 1942), 2,450 feet in the northern Pancake Range (Stewart, 1962) and 950 feet in the central Pancake Range (Mount, 1970), about 2,500 feet in the Spruce Mountain Quadrangle where it is not differentiated form the Chainman Formation (Hope, 1972), 525 feet in the northern Reveille Range (Ekren and others, 1973). 0 to 100 feet of Scotty Wash Quartzite have been mapped in the Ely and Giroux Wash Quadrangles in the central Egan Range (Langenheim and others, 1960; Brokaw, 1967; Brokaw and Heidrick, 1966), 350 to 385 feet of Scotty Wash Quartzite are present in the southern Egan Range (Kellogg, 1960), 900 feet are exposed in the Hamilton-Illipah District (Easton, 1953) and 566 to 793 feet of Diamond Peak are exposed in the central and southern Butte Mountains (Douglass, 1960; Sides, 1966). The Scotty Wash Quartzite varies from zero to about 800 feet thick in Lincoln County and is 700 feet thick in the northern Fairview Range and about 300 feet thick on Grassy Mountain (Tschanz and Pampeyan, 1970). The Diamond Peak is about 425 feet thick in the Pilot Range (O'Neill, 1968), 300 feet thick in the Leppy Range, 205 feet thick in the HD Range (Riva, 1970), estimated at 3,000 feet in the Windermere Hills (Oversby, 1969), 1,350 feet in the Wood Hills and 1190 feet in the Pequop Mountains, 5,440 feet in the Leach Mountains (LeCompte, 1978), and 1,431 feet in the southern Pequop Mountains (Robinson, 1961; Thorman 1962, 1970).

The Diamond Peak is exposed in the Diamond Mountains, Carlin-Pinon, Adobe, Peko Hills, Tuscarora, Pancake, Reveille, White Pine, Egan, Grant, Ruby, Cherry Creek, Fortification, Fairview, northern Seaman, Snake, Leppy and Pilot Ranges, Butte, Pequop, and Leach Mountains, Windermere and Wood Hills, Dutch John and Grassy Mountains, Spruce Mountain and Mountain City quadrangles.

The Diamond Peak Formation represents the late stages of clastic influx into the Antler foreland basin. The details of environment, particularly water depth, are still debated. Sillitonga (1974) and Brew (1971) for instance felt that sedimentary structures and faunal evidence in the Adobe and Diamond Ranges suggested shallow marine deltaic environments for the Diamond Peak. Poole (1974), however felt that most of the Diamond Peak as well as the Chainman Formation represented deposition by debris flows and density currents which moved shallow-water sediments into deeper marine environments as turbidites. Several workers including Sadlick (1965), Wilson and Laule (1979), and Harbaugh and Dickinson (1981) felt that the Diamond Peak or Scotty Wash represented a fluvio-deltaic sequence of sediments deposited with sedimentation in excess of subsidence within the Antler foreland. This writer concurs with the fluvial-deltaic hypothesis, rather than a deep-marine turbidite model.

Most workers agree that the upper portion of the Diamond Peak Formation has been locally reworked by fluvial systems. These lenticular upper sands commonly show climbing ripple laminae and small-scale planar and festoon-type cross-bedding and were probably deposited as point bars and various meandering stream deposits. Regionally the Diamond Peak fines to the south and east from the Adobe-Pinon-Diamond Ranges area. Paleocurrent indicatiors suggest southeast or east-southeast flow directions in the Diamond Peak (Bloomquist, 1971; Harbaugh and Dickinson, 1981).