Blue Diamond Gypsum Mine, Spring Mountains, Clark County Nevada

LOCATION (MRDS, 2011) T.21S R.59E Sec 32 36.08329 -115.3989 HISTORY AND OWNERSHIP The Mateucci Gypsum mine is a northern extension of the Blue Diamond Mine. Aerial photographs show it is vegetated suggesting that the Mateucci pit is part of an older era of Blue Diamond mine development. The early Arden mine and later Blue Diamond Mine both used tramways to take gypsum ore off the mountain and transport it to processing plants. The Blue Diamond mine is in the Ardan Gypsum District. Major gypsum producers in this district include the Arden, Bard, Blue Diamond, Honey Comb, Last Chance and Mateucci mines. Descriptions of them are found in Murphy (1954, Fig. 2), Longwell (1965:154-209), Hewett and others (1936:167, 169), USBOM, (1932, 1937, 1950), Minobras, (1973:10), and NDM (1991). MINE GEOLOGY Mining was originally room and pillar underground operation. It later became an open pit quarry An oval-shaped hill, approximately 500 feet high and three-quarters of a mile in length, the longer axis trending northwest, is underlain by gypsum. The following section is exposed at the southern end of the hill (Jones and Stone, 1920:155): Limestone, massive, dull gray, cherty, the chert in thin bands and lenses forming one-third of the mass; both chert and limestone with abundant poorly preserved fossils, the greater number being fragments of Productus and Athyris, bryozoans, and corals. 125± feet (Jones and Stone, 1920:155). Shales, red and green, gypsiferous, with thin beds of gray limestone in places and including a bed of gypsum ranging from 25 to 80 feet in thickness.: 85 ± feet (Jones and Stone, 1920:155). Limestone, gray massive with rare chert nodules; thickness unknown (Jones and Stone, 1920:155). The strata dip gently to the east, and there probably is a fault along the eastern side of the hill. A transverse fault about a quarter of a mile northwest of the quarry apparently has cut off the gypsum. The gypsum ranges from 20 to nearly 90 feet thick, the upper surface being very irregular, as shown in figure 11 (Jones and Stone, 1920:155). West of Arden, on the east side of the Spring Mountains, the gypsum is in the Permian red beds and the overlying Toroweap and Kaibab Formations (Moore, in Hewett and others, 1936, p. 167). The gypsum beds are commonly 5 to 15 feet thick, but locally may reach 75 feet in thickness. At a depth of 50 to 1oo feet from the surface the gypsum passes into anhydrite. Gypsum has been mined since 1925 in the hills near and east of Blue Diamond (fig. 20). Present production is chiefly from the upper (Harrisburg) member of tbc Kaibab Formation. Recent production is estimated to be more than 300,000 tons of gypsum annually. The reserves are large and exploration will probably reveal other large deposits. The Blue Diamond Co., a division of the Flintkote Co., operates a quarry, a plaster mill, and a gypsum lath and wallboard plant (Longwell and others, 1965:143-154).

LOCATION 35.8769 -115.46274 T.24S, R.58E, Section 29, MD B&M (MRDS, 2011) N1/2, sec. 9, T. 24 S., R. 58 E. (Longwell and others, 196, p. 187). DEVELOPMENT Recorded production (1912 1916) equals: 9,773 lb lead, 3,275 lb copper, 2,550 lb zinc, 125 oz silver, 1 oz gold, about 78 lbs cobalt (Hewett, 1931)(Longwell, 1965, p. 187, table) . GEOLOGY Lenses of ore in crushed Bullion Dolomite member above the Contact thrust (Carr and Pinkston, 1987). MINERALOGY The deposit is interesting because it has yielded unusual mineral specimens. At one place some drusy cavities yielded excellent crystals of malachite, pseudomorphous after azurite, as much as an inch long. In 1921 cobalt minerals were recognized on the dump, and A. Woodard, of Las Vegas, mined the cobalt bearing material recorded below. In the material on the dump heterogenite was common, in part replacing the dolomite wall rock and in part forming slender stalactites, on some of. which quartz has been deposited. Some specimens show a pale-pink dolomite that cements gray dolomite. Blowpipe tests show that the pink dolomite contains an appreciable trace of cobalt (Hewett, 1931, p. 110).

LOCATION 12N 17E Sec. 33 SBM 35.08113000020 -115.15055 (MRDS, 2011) 12N 17E Sec. 33 SBM 35.08171999970 -115.15023 (MRDS, 2011) 12N 17E Sec. 33 SBM 35.08113000040 -115.15111 (MRDS, 2011 “Unnamed” Mine). This mine is in the Bobcat Hill, a northwestern extension of the Vontrigger Hills. 1953 Section 22?. T.12N, R.17E, SBM, North of Goffs (Wright and others, 1953, Gold Table, Map No. 193, p. 60). 1964, 1987 Location: NE1/4 Sec. 33, T.12N ., R.17E., SBBM, San Bernardino Co. (Southern Pacific, 1964c, 1964d; Oesterling and Spurck, 1964, p. 128; Tishler and Boham, 1960a, 1960b). Also in MRDS as “Unnamed” mine. 1990 T.12N, r.17 E, Section 33 SBM (U.S. Bureau of Mines, 1990a, Table 2, Map No. 588, p. 195). OWNERSHIP Fred cram, Box 6, Ivanpah, California (Wright and others, 1953, Gold Table, Map No. 193, p. 60). DEVELOPMENT 1911 Mr. Harwood Robbins, a nephew· of J. D. Rockefeller. Mr. Tucker of Riverside [California] who is heavily interested in the California Gold &. Copper Co. and an expert made a visit to the True Blue property and were well satisfied. They purchased a· fifteen horsepower hoist from the Vontrigger. Mercantile Company and also ordered timbers and all material and expect to work as soon as possible (Los Angeles Mining Review, 1911, June 8). 1953 Developed by several shafts; one shaft 100 ft. with 200-ft. drift at bottom. Single stamp mill on property. Owner reports Albert Cram, father, produced $40,000 from property in early 1890's. Latest production, 7 tons gold ore in 1936. Idle (Wright and others, 1953, Gold Table, Map No. 193, p. 60). 1964, 1987 Description: at least seven shafts to 125 feet deep with several hundred feet of drifts; reportedly yielded $40,000 in gold in early 1890's and seven tons of gold ore in 1936 (Southern Pacific, 1960; Oesterling and Spurck, 1964, p. 128; Tishler and Boham, 1960a, 1960b). 1990 Workings consisted of five shafts (one 30 feet deep) and about six pits. Most workings and dumps have been bulldozed shut and no trace of possible ore exists. No evident trenches or zones exist on the surface. (U.S. Bureau of Mines, 1990a, Table 2, Map No. 588, p. 195). GEOLOGY OF THE VONTRIGGER HILLS The geology of the Vontrigger Hills was described by Ted Theodore (1996, p. 121): Bedrock of the Vontrigger Hills is mostly Early Proterozoic granitoid rocks (unit Xg1, pl. 1), dated between 1,660 and 1,695 Ma, and migmatite (Xm). Small areas of Miocene volcanic rocks (Tv1) and Cretaceous granitoid rocks (Kpg) are found mainly in the western part of the area. Stream-sediment samples from the Vontrigger Hills do not contain anomalous concentrations of any elements. However, concentrate samples have anomalous concentrations of Ag and Ba, and rock samples have anomalous concentrations of Cu, Mn, Pb, Zn, Ag, As, Bi, Mo, Be, B, and Nb. The area is geochemically moderately anomalous overall. Possible deposit types include porphyry copper-molybdenum, polymetallic veins and replacement bodies, and REE-Nb-bearing pegmatites (Theodore, 1996, p. 121). Six mineral occurrences in the Vontrigger Hills include three polymetallic veins, two low-sulfide gold-quartz veins, and one polymetallic fault (pl. 2). All occurrences are far removed from the Cretaceous granitoid that crops out near the southwest end of the Vontrigger Hills (pl. 1), and all the occurrences are hosted by Early Proterozoic younger granitoid rocks. Mineralization is extremely widespread at some localities (pl. 2), such as in the general area of the Rattlesnake Mine (U.S. Bureau of Mines, 1990a, map no. 592, pl. 1), where numerous prospect pits, shafts, and a partially reclaimed open cut approximately 100 m wide follow favorable indications of gold mineralization of various attitudes and types in an area of about 3 km2. Much of the gold mineralization initially exploited at the Rattlesnake Mine, classified as polymetallic vein, is along a 10-m-wide zone of intensely silicified and highly fractured, foliated Early Proterozoic younger granitoid rocks. This mineralized zone has a strike of about N. 70° W. and is present at the north edge of a porphyritic monzogranite of undetermined size (not shown on pl. 1). Numerous unmineralized porphyritic granite dikes containing K-feldspar phenocrysts cut the Early Proterozoic younger granitoid rocks (Theodore, 1996, p. 121). MINE GEOLOGY 1953 Narrow gold-bearing quartz stringers in Archean metamorphic rocks (Wright and others, 1953, Gold Table, Map No. 193, p. 60). 1956 Hewett’s map (1956) has the True Blue Mine surrounded on three sides (east, west, south) by (Tfs). The True Blue Mine is in PreCambrian gneiss and granite (€g). 1960 Tishler and Bonham (1960a) mapped the area of the True Blue mine as Pre-Cambrian Granite – gneiss (p€gr). Tishler and others (1960b) said this of the Vontrigger Hills gneissic granite: …cropping out in the Vontrigger Hills as well as the Tungsten Flat Signal Hill area is gneissic granite. This granite, which ranges in color from light bluish gray (5 B 7/1) to medium bluish gray (5 B 5/1), is composed largely of coarse orthoclase crystals (1/4" long) in a sheared and rolled quartz and biotite matrix. In the Vontrigger Hills the granite gneiss is intruded by quartz monzonite porphyry dikes and crushed granite porphyry dikes which are composed of rounded orthoclase, biotite,and sericite (Tishler and others, 1960b, p. 12) 1964, 1987 Geology: gold, chalcopyrite, malachite, and azurite in narrow quartz veins in steeply dipping shear zones that trend NW in gneiss Conclusions: shows limited promise. (Southern Pacific, 1960; Oesterling and Spurck, 1964, p. 128; Tishler and Boham, 1960a, 1960b). 1990 Precambrian granitic rocks · Metamorphosed with chlorite and malachite/azurite staining on dump. Extensive evidence of hydrothermal alteration. (U.S. Bureau of Mines, 1990a, Table 2, Map No. 588, p. 195). Four samples, CAL 4·S and 30·31, taken from selected material from dumps. Malachite/azurite chloritized Precambrian granitic rocks. No visible sulfides. Samples contained up to 8,440 and 4,S60 ppb gold and 0.8% and 0.6% copper (U.S. Bureau of Mines, 1990a, Table 2, Map No. 588, p. 195). 2007 Miller and others (2007) mapped the rocks at the True Blue mine as Younger Proterozoic granitoids (Xg1)

LOCATION 35.82028 -115.4761 24S 58E Sec 33 (MRDS, 2011) 35.8206 -115.4758 24S 58E Sec 33 (MRDS, 2011) N1/2, Sec. 33, T. 24 S., R. 58 E. (No. 43, pl. 30)(Hewett, 1931, p. 121; Longwell and others, 1965, p. 188, table).The Columbia Mine is near the Columbia Pass (Albritton and others, 1954, p. 13). DEVELOPMENT The Josephine claim was located in 1883, but most of the work is on the Columbia claim, which was located in 1886.· According to local report, a prospector, Von Trigger, had located the ground and mined 10 tons of copper ore as early as 1880. From 1898 to 1903, when the Columbia and Boss mines were optioned to Emory Hershing and associates, there was some exploration and a mill was built on the present site of the Yellow Pine mill. This was the first mill erected in the district. In 1906 the property was bought for $20,000 by Joseph Dederich, who still owns it (Hewett, 1931, p. 121 and 129). Recorded production (1906 • 1954) equals: 653,043 lbs. copper, 6,481 oz silver, 30,007 lbs. zinc, 54 oz gold. About 919 lbs. of cobalt oxide was shipped in 1921. Hewett 1931, p. 121-122; 1956, p. 133-134 (Longwell and others, 1965, p. 188, table). GEOLOGY Ore bodies in dolomitized zones above a granite porphyry sill near the middle of the Sultan Limestone. Chalcopyrite, chalcocite, and tenorite composed the ore above the sill. Some heterogenite occurred along fractures (Longwell and others, 1965,p. 188, table). MINERALOGY Ore bodies in dolomitized zones above a granite porphyry sill near the middle of the Sultan Limestone. Chalcopyrite, chalcocite, and tenorite composed the ore above the sill. Some heterogenite occurred along fractures (Longwell and others, 1965,p. 188, table).

LOCATION 35.76694 -115.45220 25S 58E Sec 15 (MRDS, 2011, “Monte Cristo”) 35.76670 -115.44190 25S 58E Sec 14 (MRDS, 2011 “Combination Lode”) Sec. 14, T. 25 S., R. 58 E. (Longwell and others, 1965, p. 193, table) There is a disagreement between the MRDS database and USGS topographic maps. The placement of the Monte Cristo on the 1:24,000 topographic map is the location of the “Combination Lode” mine in MRSD (2011). The Monte Cristo mine (No. 58, pl. 30) is on the west side of Porter Wash 4 miles due south of Goodsprings (Hewett, 1931, p. 156). PRODUCTION Total recorded production (1908-1919) equals: 6,386,802 lb zinc (Hewett, 1931, p. 156-158; 1956, p. 152; Albritton and others, 1954, p. 68)(Longwell and others, 1965, p. 193, table). GEOLOGY The deposit is uncommonly interesting because only Zinc ore was encountered, and it was an exceptionally concentrated body, as one may readily suspect by the size of the workings and the meager dump. It lies wholly in the cherty Anchor limestone of the Monte Cristo formation,· which is not as extensively dolomitized here as farther north. The limestone is well shown several hundred feet east of the mine, where the color is blue-gray. and the texture [is] dense and porcelainlike. It contains ·conspicuous· layers of dark chert nodules. The strike is nearly north and the dip 25° W. The deposit is located between two faults that strike N. 35° W. and dip 50° NE. (See fig. 6.) Doubtless these faults were formed after the zinc sulphide deposit was introduced but before most of the oxidation to carbonate and silicate had taken place. They have been traced several thousand feet southeast (Hewett, 1931, p. 157). "J" shaped ore body in dolomitized Anchor Limestone Member; about 280 feet long, 40 feet wide, and 8 to 20 feet thick. Ore nearly pure smithsonite at one end and calamine and hydrozincite at the other end (Longwell and others, 1965, p. 193, table). MINERALOGY In 1912, Hill (1914, p. 271) observed mining in the area of the present glory hole. He reported that the ore was nearly pure white smithsonite. That some hydrozincite was mined in this area was, however, assumed by Hill, who noted the mineral in crop pings around the stope. This assumption was later substantiated when appreciable tonnages of the hydrozincite ore were sorted from the dump (Hewett, 1933m p. 157).·Nevertheless the reports seem to agree that the ore was largely made of smithsonite at the north and of calamine and hydrozincite at the south. Whether there was any zonal arrangement of the calamine and hydrozincite is uncertain (Phoenix and Richards, 1954, p. 69-70)

LOCATION (MRDS, 2011) TRS Latitude Longitude T.20S R.63E Sec 34 36.164390 -114.93440 [The North Rainbow Gardens Gypsum Mine is] in the SW /4 Section 34, T.20S, R.63E, in the northern part of Rainbow Gardens, 3.0 miles northeast of the White Eagle gypsum mine. The North Rainbow Gardens Gypsum mine is in the Las Vegas Mining District (Tingley, 1998). HISTORY The North Rainbow Gardens Gypsum mine does not appear in Longwell and others (1965:204 Appendix B. Tabulation of gypsum mines in Clark County). Gypsum mining at the North Rainbow Gardens mine (fig. 6), about 5 km northeast of the White Eagle mine, began in the late 1950s (Papke, 1987). Fibreboard Paper Products was the operator at this mine (referred to by the U.S. Bureau of Mines as the “Henderson” operation). In 1959, the company switched its mining operations from the Rainbow Gardens area to the PABCO mine about 7 km to the northeast (see below). The North Rainbow Gardens mine was mostly idle until the late 1980s, when it was again operated by Nevada Gypsum and Mining and Nevada Gypsum, Inc. The last mining activity recorded at the property was in 1993 (Castor, 1994)(Castor and others, 2006, p. I4. OWNERSHIP The North Rainbow Gardens Gypsum mine is on land administered by the Bureau of Land Managemen. GEOLOGY The North Rainbow Gardens Gypsum Mine is in a north-northeast to south-southwest trending belt of the Gypsum-rich sequence of the Thumb Member of the Horse Springs Formation (Ttg). Aerial photographs show the mine to be mostly in the Horse Springs Formation. The mine is at the southwest projection of a syncline.

LOCATION 35.84417 -115.49501 (MRDS, 2011) 35.8425 -115.49694 (MRDS, 2011) Section 20 and 29, T. 24 S.,R. 58 E (Longwell and others, 1965, p. 186, table). The Alice (Yellow Pine Extension) Mine is 2,500 feet south of the Yellow Pine Mine and 4,500 feet southeast of Shenandoah Peak on the eastern flank of the Spring Mountains. DEVELOPMENT Intermittent production from 1909 to 1924. Total production equals: 1, 528,851 lb zinc, 46,600 lb lead, 30,933 lb copper, 1,141 oz silver (Hewett, 1931, p. 138-139). GEOLOGY The bodies of the Yellow Pine and Alice mines are tabular pipes (Hewett, 1931, p. 93). The main shaft is sunk in beds of the Bird Spring formation that lie 100 feet or more above the base. In this area they are largely converted to dolomite. Even though they strike generally northwest and dip southwest, they are locally folded and much faulted. At three places in the mine sill-like masses of granite porphyry have been met. The shoots that have been the sources of ore underlie a persistent wall that lies only a few feet above the middle of the sills. In a broad way the wall conforms with the bedding; locally it cuts across it (Hewett, 1931, p. 138). The Alice mine has a nearly continuous ore shoot 900 feet long, up to 40 feet wide, and 2 to 5 feet thick in dolomite in the basal Bird Spring Formation. Hydrozincite was the ore mineral; aurichalcite, cerussite, and a vanadate were common; galena was uncommon (Longwell and others, 1965, p. 186)

Prospecting at the Yellow Pine Mine began as early as 1857. The Yellow Pine mining district was organized in 1882. Oxidized copper ore was shipped in 1906 and small bodies of lead and zinc were discovered in 1907. A narrow-gauge railroad arrived in 1910 and that connected the mine to the standard gauge line of the Union Pacific Railroad connecting Las Vegas and Mojave. In 1912 the Hale shaft was deepened to expose several more lead-zinc orebodies. The peak of production came during World War I, when the camp was the principal source of zinc in the State of Nevada. In 1916, when conditions in the southern part of the mine were discouraging, exploratory work from the vertical shaft in the northern part of the third level encountered the. ore body in the 350-foot stope, and from that tune the development has been progressively northward. Early in 1922 most of the ore known south of the porphyry dike on the 900-foot level had been mined, when a raise· from the 900-foot level north of the dike struck two large bodies of ore. The company then sank the new vertical shaft (completed January 1924). There was little mining during the interval 1921-23. After a wave of renewed activity beginning in 1924 and continuing for 4 years. The Yellow Pine Mining Company owned 12 claims in the ravine known as Porphyry Gulch in 1931. Up to 1931, when operations ceased, the average content of the products shipped each year shows that the crude lead ore has contained 47 to 63 per cent of lead, 5 to 13 per cent of zinc, and 17 to 22 ounces. of silver to the ton. The lead concentrate has contained 51 to 56 per cent of lead., 12.5 to 14.5 per cent of zinc, and 25 to 50 ounces of silver to the ton. The district was virtually dormant until the outbreak of World War II. The U. S. Smelting, Refining, and Mining Exploration Co. took lease and option from the Yellow Pine Co. in 1934, resuming operations that have continued intermittently until the present, though under different managements. In 1936 the lease passed to C. K. Barns, and in February 1939, the property was taken under lease and option by Harold Jarman. From May until December 1942, Basil Prescott held the property under lease from Jarman. From September 1942, to January 1943, 64 core-drill holes having a total length of 5,161 feet were drilled by the U. S. Bureau of Mines. In December 1942, the lease and option passed to the Coronado Copper and Zinc Co., which continued operations until the spring of 1949. In 1944, the Bureau of Mines carried out a second exploration project, drilling 35 core-drill holes with a total length of 5,113 feet. At the end of 1944 the district had produced about 93,000 tons of zinc and 37,000 tons of lead. In 1943-44 ore was purchased at premium prices by the Metals Reserve Co. and stored at Jean station on the Union Pacific Railroad. After 1950, considerable exploration work was done, and intermittent attempts since then have been made to re-open the mine. The mine is hosted by dolomitized breccia zones in the Yellow Pine and Anchor Members of the Monte Cristo Formation. Many ore deposits occur in or adjacent to granite porphyry dikes. The porphyry intrusions are tens to hundreds of feet wide in plan with 64 to 70 percent SiO2 and variable amounts of K2O, CaO, Na2O, and MgO. The ore bodies of the Yellow Pine are tabular pipes which form at the intersection of low angle thrust faults and high angle faults. The high-angle faults were the conduits for ore fluid introduction to the host rocks. The sequence of structural events at the Yellow Pine mine are: (1) Folding and earliest thrust faulting Contact, Potosi, and Wilson faults; (2) intrusion of Yellow Pine sill; (3) transcurrent faulting along northwest faults and Alice and other northeast faults; (4) intrusion of Yellow Pine, Alice, and Red Cloud dikes; (5) deposition of the ores (6) post-ore faulting. The Yellow Pine ore deposits have been oxidized. Hydrozincite is the primary Zinc sulfide and galena the primary Lead sulfide Materials remaining in the stopes indicate that most ore was a porous aggregate of calamine crystals and hydrozincite pods and stringers, containing accessory masses of cerussite surrounding nuclei of galena, all stained to some extent with iron oxide. Malachite is commonly present as minute flecks and films; where it.is locally abundant, iron oxide is generally abundant also. Presumably the primary ore bodies were made up principally of sphalerite and galena, and minor amounts of other sulfides. Subsequent to deposition the ore has been oxidized to an unknown depth below the deepest workings in the mine. Sphalerite changed to hydrozincite (2ZnC03.3Zn(OH)2), calamine (H2ZnSi05), and smithsonite (ZnC03). Within the ore bodies galena remains the only observed representative of the primary minerals, but in many places it too is altered, either partly or completely, to cerussite (PbC03 ) and anglesite (PbS04). At the Yellow Pine, there was a late Paleozoic mineralizing event, possibly Mississippi Valley-type mineralization, that created the original sulfide zinc-lead replacement deposits in Monte Carlo Fm limestones. Then in the late Triassic there was a mineralizing period that lead to formation of the precious metal and other ore types and also remobilized the Paleozoic lead-zinc deposits. The parent porphyritic intrusion for this late Triassic event has not been exposed. It may have been displaced by crustal extension in the Miocene.

LOCATION 35.8269 -115.49254 (MRDS, 2011) T.24S, R.58E, Sec. 29 MD B&M (Longwell and others, 1965, p. 187, table). The Bell Mine is 900 feet west-southwest of an active mining operation at the Cosmopolitan mine. GEOLOGY These workings explore a silicified shear zone that strikes N. 60° W. and dips 80° NW.; the country rock is. the Bird Spring formation. The local rock exposures indicate· that the shear zone lies in a block of dolomitized Bird Spring limestone that overlies the Contact thrust and is limited on the south by the Keystone thrust and on the west and east by later normal faults. If extended 100 feet farther, the deepest shaft would pass into beds under the Contact thrust, probably the lower part of the Moenkopi formation. (Hewett, 1931, p. 111). MINERALOGY The dump material shows considerable manganese oxide and small quantities of chrysocolla and a yellow vanadate (Hewett, 1931, p. 111).

LOCATION 35.84 -115.53251 (MRDS, 2011) 35.8397 -115.53274 (MRDS, 2011) T.24S, R.57E, Section 24 (Longwell and others, 1965, p. 188, table) On the Chaquita claim (No. 21, pl. 30), 3,000 feet west of the Keystone [Mine], nearly 1,000 feet of work has been done. PRODUCTION Only recorded production (1937-1939) equals: 30,864 oz gold, 19,108 lbs copper, 2,141 oz silver, 18,290 lbs lead. Hewett. 1931, p. 104, 1956, p. 123 (Longwell and others, 1965, p. 188). GEOLOGY Ore in siliceous limonite lenses parallel to bedding near the middle of the Goodsprings Dolomite (Longwell and others, 1965, p. 188, table). In proximity to granite porphyry intrusive MINERALOGY In the Clementina, Chaquita, and other near-by prospects [gold] seems to have been closely associated with limonite, doubtless derived from pyrite (Hewett, 1931, p. 80).