Copper Creek Project

  • Overview
  • Geology
  • Location
  • Property History

Copper Creek

Copper Creek is a large “Early Halo” Porphyry Copper Deposit, located 75 road miles northeast of Tucson and 15 miles northeast of San Manuel, in an area well situated in regard to existing general and copper mining infrastructure. The current resource area is ~4km in length and open in all directions. Ongoing work programs have resulted in extensive geological, geochemical and geophysical databases. Over 670,000 feet of drilling has been completed and is ongoing. Copper Creek property consists of approximately 16 square miles of contiguous patented and un-patented mining claims and state prospecting permits. The area is a mining friendly and politically secure location with excellent and readily accessible infrastructure including power, rail, water, roads and qualified consultants.

The property is in the prolific southwest porphyry copper belt at the projected intersection of a major northwest belt of porphyry copper deposits (Ray, Miami/Globe, Superior/Resolution, Johnson Camp) and a major east-northeast belt of porphyry deposits (San Manuel/Kalamazoo, Silver Bell, Lakeshore, Safford, Morenci). The property is within sight of the former BHP Kalamazoo copper smelter and mine and within 30 miles of an existing operating copper mill and smelter. The area is a mining friendly and politically secure location with excellent and readily accessible infrastructure.

Copper Creek hosts multiple Breccia and Porphyry Copper Deposits. Both deposit types include current copper/molybdenum resources prepared in accordance with CIM standards. Molybdenum is present in varying amounts in the Breccia and Porphyry Copper deposits and is expected to provide substantial credits to both deposit types. Gold and silver are also present in both deposit types and are expected to provide credits during mining.

The Copper Creek property has had a substantial amount of exploration conducted on it, with 480 drill holes and 670,000 feet of drilling to date, and there is significant potential for additional discoveries on this large claim block. Development to date on the property has been confined to the original 7 square miles highlighted by the inset block in Figure 1. There are over 400 known breccia deposits on the 5,100+ acre original Copper Creek property, of which only about 35 have had drilling on or near them and only 8 are included in the resource and have been adequately drill tested. A multitude of other high-potential target exploration areas have been identified in this prolific area of breccia outcrops with more than 80% of the original property and all of the new 22 square mile addition still open to further exploration.

Redhawk engaged Tucson, Arizona based Independent Mining Consultants (“IMC”) on multiple occasions to calculate, in accordance with CIM standards, Mineral Resource tons and grade for the porphyry and breccia deposits. The most recent resource calculation was completed in December, 2012. Full details of the resource calculations and the complete Technical Reports are available under the tab “Mineral Resource Estimate” on this website.

Redhawk believes that a combination of the higher-grade breccia deposits and the much larger porphyry deposit represented by the Keel and American Eagle deposits offer an opportunity for developing a large low cost, long life mining operation. Redhawk, through its consultants, completed the ground water monitoring, waste rock characterization studies, environmental and cultural studies required to submit an Aquifer Protection Permit (APP) with the Arizona Department of Environmental Quality to allow an exploration and development decline to be driven into the Breccia Resource area. That permit application was approved in 2009 and is the key permit to allow underground access at Copper Creek.

Redhawk’s consultants completed a Scoping Study in 2009 which was subsequently updated in 2010. The Scoping Study was based on the 2008 resource report and was based on the best information available about the deposit at that time. It was developed around a very conservative smaller scale underground mine achieving a maximum throughput of 10,000 tons per day. Even at the smaller scale the operation achieved a NPV of US$350m at a 7.5% discount rate pretax. The complete Scoping Study is available in the website under the tab “Properties-Copper Creek — 2010 Scoping Study”.

During 2011 and 2012 Redhawk completed a number of initiatives designed to provide sufficient information to commence a new Preliminary Economic Analysis (PEA) in late 2012. This included a 30,000 meter drill program; oriented core and additional geo-tech work; hydrology studies; advanced metallurgical studies; and the completion of the environmental studies to cover the entire original 7 square mile property. The initial part of the study will be to review different surface and underground mining approaches and determine the best mining technique for Copper Creek. Following this trade off review the PEA continued with the selected underground mining approach.

An amended PEA was completed in October 2013 and was developed around a 25,000 short tons per day (tpd) underground room and pillar/post pillar primary operation in the porphyry deposit, room and pillar/post pillar and cut and fill mining in the breccia resources, and open pit mining of the Old Reliable breccia resource.  Processing is a conventional copper flotation concentrator with a molybdenum separation circuit.  The project produces a US$488m NPV at a 7.5% discount pretax and a 16% IRR at US$3.30 copper price.  Copper production is estimated at 121 million pounds (55,200 metric tonnes) per year at a cost of US$1.74 per pound of copper net of byproducts.

The cash flow analysis in the PEA is pre-tax. If the project is profitable, Redhawk would be subject to tax in the State of Arizona. For financial planning and budgeting purposes, combined federal and state corporate income taxes have been estimated at 39.53 percent.

The PEA is preliminary in nature and it includes inferred resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as mineral reserves.  There is no certainty that the PEA will be realized.

Geology

The Copper Creek area, part of the Bunker Hill District, Pinal County, Arizona, lies on the west side of the Galiuro Mountains, 75 kilometers (45 miles) northeast of Tucson. The district lies in the heart of the southwestern U.S. porphyry copper province, at the intersection of important belts of deposits trending NW-SE (Miami-Globe, Resolution, Ray, Bisbee) and WSW-ENE (Lakeshore, Silver Bell, San Manuel-Kalamazoo, Safford, Morenci).

The district is centred on the Copper Creek granodiorite, the central of three Laramide granodiorite intrusions forming a northwest-oriented cluster. The Copper Creek granodiorite was emplaced approximately 62 million years ago into Precambrian and Paleozoic sedimentary rocks, Late Precambrian diabase, and Cretaceous Glory Hole volcanics. The Copper Creek stock and adjacent Glory Hole volcanics have been intruded by a sequence of Laramide granodiorite, monzogranite, and quartz diorite porphyry plugs and dykes. The district is marked by over 400 hydrothermal breccia bodies, ranging from a few feet to several hundred feet across, which (like the porphyry bodies) are concentrated in two northwest-trending belts (see map). Post-mineral, mid-Tertiary Galiuro Volcanics cover all these rocks on the east and northeast. To the southwest, the district is bounded by a northwest-trending range-front fault which downdrops Tertiary Gila Conglomerate against the Laramide and older rocks.

The Copper Creek area contains multiple styles of Laramide copper-molybdenum-silver +/- gold deposits characterized by relatively high primary copper grades. Early development of the district dated from 1863, and focused on the exposed copper-rich (>>1% Cu) breccia bodies and peripheral silver-lead-zinc veins. In the 1960s and 1970s deeper drilling discovered porphyry-style sheeted and stockwork vein mineralization (~0.8% Cu) at depths between 350 and +1,200 m (1,200 to +4,000 feet) in the American Eagle and Keel areas, beneath a small portion of the near-surface breccia cluster.

The breccias are clast- to matrix-supported and consist of angular to subrounded, pebble- to boulder-sized, commonly quartz-sericite altered fragments formed from the host wall rock. Matrices of most breccias are partially to completely filled with varying combinations of quartz, pyrite, chalcopyrite, bornite, molybdenite, tourmaline, specularite, and minor rock flour. The upper levels of some breccias also contain chalcocite. High-grade mineralization in the breccias typically occurs as prominent coarse masses and clots of copper minerals filling open spaces, or as sheeted veins along the edges of the pipes. Relative levels of copper, molybdenum, gold and silver vary considerably from breccia to breccia. Molybdenite Re-Os ages from the breccias yield mineralization ages between 62 and 57 million years.

Breccias are known to persist over 1000 meters vertically. They terminate abruptly upward into lower grade material; the Mammoth pipe, the largest breccia in the current resource, is “blind” a mere 32 meters below the surface. Where drilling density is sufficient, the bottoms of the breccia pipes neck downwards into bodies of granodiorite porphyry. Over 90 percent of the mapped breccia bodies have not been drilled.

The American Eagle and Keel porphyry zones were previously classified as “hybrid porphyry” or “sheeted vein type” deposits due to their unusual vein styles. Recent work by Redhawk geologists has led to the recognition that the Copper Creek porphyry ores are typical of the “early-halo type” of porphyry system (Proffett, J.M., 2009, Geology, v. 37, p. 675-678). In these deposits the dominant style of copper-bearing veins are early dark micaceous (EDM) veins or early potassic halos lining incipient fractures, rather than the A-type sugary quartz stockwork veins common in many porphyry systems. Well known early-halo type porphyry deposits include Butte, Montana, and Chuquicamata and Los Pelambres, Chile.

Recent drilling indicates the American Eagle and Keel porphyry-style resources are connected and form a single copper-mineralized body at least 1,500 meters long northwest-southeast, which is open in most directions. This mineralized body is controlled by a broad dome-shaped zone of common, subhorizontal to steep EDM quartz-sulfide veins with halos of biotite, sericite, and abundant copper sulphides. The EDM vein zone is hosted mostly in Copper Creek granodiorite but appears centred on a cluster of syn-mineral granodiorite porphyry bodies. Superimposed on the EDM vein zone are breccias and zones of intense quartz-sericite alteration, both of which tend to carry high-grade copper which upgrades the same volume of rock. A near-vertical set of EDM veins extends above the well mineralized dome-shaped EDM vein zone to the present surface, where outcropping veins are widespread and typically trend east-northeast. Sulfides are zoned with depth, with pyrite-dominant mineralization near the surface transitioning into chalcopyrite-dominant rock in the better mineralized zones, with increasing bornite at depth.

Location

The Copper Creek property is one contiguous group of patented, unpatented Federal claims and Arizona State Mineral Prospecting Permits totalling approximately 29 square miles. Copper Creek lies within the porphyry copper metallogenic province of the southwestern United States in an area with a long history of copper mines. There are several large adjacent properties that have been or still are major producers of copper. The San Manuel/Kalamazoo deposit lies within 15 miles of the Copper Creek Property. San Manuel was a major underground copper mine until its closure, with production in excess of 50,000 short tons per day.

Copper Creek is located 75 road miles northeast of Tucson and 15 miles northeast of San Manuel. Tucson is a major population center (approximately 700,000 persons) and transportation hub with well developed infrastructure and services to support the surrounding copper mining and processing industry. Access to the property from Tucson is by paved highway for 65 miles to the property road junction, then for 10 miles on gravel roads to the site. A network of ranch and mine roads provide access throughout the property to existing drill sites and the old mine workings.

The area has well developed infrastructure for mining. The closest operating mining complex is the ASARCO Ray mine located near Hayden, 30 miles northwest of Copper Creek on Highway 77. At Hayden, ASARCO operates one of the two copper smelters located in Arizona. The Copper Creek Project has good road and railroad access, access to electrical power and water within a few miles of the property and a skilled labor force in the surrounding area.

The elevation on the property ranges from 3,400 to 4,900 feet above mean sea level in rugged terrain of the eastern Basin and Range physiographic province of southeastern Arizona. The climate varies with elevation, but in general the summers are hot and dry and winters are mild. The area experiences two rain seasons in general, one during the winter months of December to March and a second summer season from July through mid September. The summer rains are typical afternoon thunderstorms that can be locally heavy. A rain gauge maintained on Copper Creek since 1987 has recorded annual rain amounts ranging from 8.94 to 24.7 inches with an average close to 13 inches per year. Occasional light snow falls at higher elevations in the winter months. Exploration programs and mining operate year around in the region.

Property History

The history of the Copper Creek Property goes back some 140 years with the Bunker Hill (Copper Creek) mining district being organized around 1883. Claims were staked to cover copper deposits prior to 1900, but little work was done in the district until after 1902. Most of the interest in this property came as a result of the massive outcropping of breccias that was evident to even the unsophisticated miner. By 1913, the Copper Creek Mining Company and its successors (the Minnesota-Arizona Mining Company and Copper State Metals Mining Company) had constructed a dam, power plant, dispensary and 200 ton/day gravity concentrator and had developed and mined a small ore body at American Eagle and the Old Reliable. About 30,000 tons were produced prior to shutdown in 1919.

Commencing in 1907, the Calumet and Arizona Mining Company (C & A), guided by Ira Joralemon, explored the Copper Giant, Copper Prince, Glory Hole (Globe), and Superior pipes by adits, shafts and drifts. To supplement the underground exploration, C & A drilled about 6,000 feet in fourteen surface holes during 1914. A copper resource was found in both the Glory Hole and Prince pipes, but there was no production. Title passed to Phelps Dodge Corporation in 1931 when it purchased the Calumet and Arizona Company (C&A). The only recorded production from the C & A ground has been by Arizona Molybdenum Corporation which mined and milled 23,312 tons from the Copper Prince pipe with average grade of 3.19 % Cu during 1937. Written logs of the C & A drill holes reside in Redhawk’s files, but core has not been located.

An adit, driven below the outcrops of the Childs Aldwinkle pipes in 1915 discovered the copper-molybdenum ore body there and the pipes were partly developed for production during 1917 — 1918; the claims were surveyed in 1916 and patented in 1919. Arizona Molybdenum Corporation acquired the property in 1933 and proceeded to develop the copper and molybdenum ore body to 520 feet below the haulage level. Between 1933 and 1938 about 329,000 tons were milled.

In 1959, Bear Creek Mining Company (Kennecott) optioned the Siskon ground and also the Childs Aldwinkle patented claims. Bear Creek mounted the first integrated exploration (geologic mapping, geochemical and geophysical surveys, followed by drilling), at Copper Creek. Fifteen holes were drilled there by Bear Creek and several of these cut mineralized zones. However, none of the Bear Creek intersections appeared to be minable and they abandoned the project in 1962. The Bear Creek drill core was stored in a cabin at the Old Reliable under care of watchman Pete Carey. This core was moved to a warehouse at Magma’s plant in San Manuel in 1967 and is now in the possession of Redhawk.

In 1966, Newmont Exploration Limited (NEL) optioned the Siskon property and enlisted Magma Copper Company (80.3 percent owned by Newmont Mining Corporation) as co-venture and operator. The Childs Aldwinkle patented claims were also optioned, as were adjacent claims owned by Clark, Downey and Lehman as well as the patented Redbird claims (Bluebird mine). Additional claims were located to cover open Federal land and State land was leased. This land package forms the bulk of the property Redhawk holds at Copper Creek, today.

By this time exploration was being directed toward discovery of a major disseminated copper deposit and the breccia pipes were no longer the primary target. Between 1966 and 1970, geology of the district was mapped and 30 deep core holes were drilled. Core from these and all other JV holes drilled at Copper Creek was stored in a warehouse at Magma’s plant at San Manuel, until June 2005. This work demonstrated a significant copper-mineralized zone, at depth, beneath the American Eagle Area. Magma became a wholly-owned subsidiary of Newmont in 1969.

In 1968, Occidental Minerals Corporation (Oxymin) leased some of the land and optioned part of the adjacent Phelps Dodge ground that covered the mineralized Glory Hole, Copper Prince and Copper Giant breccia pipes. The old workings that C & A had driven to test the Phelps Dodge pipes were rehabilitated above the water table and Oxymin drilled 67 surface and underground holes to test the Old Reliable, Glory Hole, Prince and Giant pipes. Oxymin released their option on the Phelps Dodge ground in about 1970. Redhawk has copies of Oxymin core logs, but no logs for percussion holes; location of the core is not known.

Oxymin, in 1971, assigned their interest in the Old Reliable to Ranchers Exploration and Mining Company (Ranchers). Ranchers drilled three holes to confirm results of Oxymin drill holes; logs of the Ranchers holes are in Redhawk’s file, but location of the core is not known. In 1972, Ranchers, in association with Du Pont, rubblized the Old Reliable pipe above the 3730 elevation, by blasting with ANFO. Copper was leached from this rubble-column with dilute sulfuric acid; copper was recovered from the leach-liquors by precipitation on tin-cans in a plant below the mine. More than 12,077,000 pounds of cement copper were recovered between 1972 and 1981, when Ranchers’ lease expired.

In the years 1972 — 1974, after retrieving its property from Oxymin, Phelps Dodge geologists mapped, sampled and tested the Phelps Dodge ground with geophysics; nine holes were drilled to test deep targets, with disappointing result. Phelps Dodge did not explore the breccia pipe deposits on its ground. Redhawk has copies of the Phelps Dodge drill hole logs. Phelps Dodge has the core.

Humble Oil joined Newmont and Magma in exploration for porphyry copper deposits at Copper Creek in 1971. Humble assumed project management during 1971-1972 (their “earn-in” period) and drilled 20 deep holes. It was Humble-Newmont hole HN-12 that discovered the third (north) finger of the Childs Aldwinkle pipe. Redhawk has both logs and core. Humble Oil was renamed Exxon Corporation in about 1973.

Newmont resumed management of the Copper Creek Joint Venture in 1973 and drilled six angled holes from surface to test pipe targets. However, by the mid-1970s, Newmont’s corporate interest in porphyry copper exploration had waned. The Copper Creek project reverted to care and maintenance; drill targets were carefully selected, but drilling was reduced to the amount needed to underwrite property maintenance costs (assessment work). Hole NE-6 discovered the lower Mammoth feeder-zone and hole NE-10 discovered the Mammoth breccia pipe. Redhawk has both logs and core for these holes. Between 1972 and 1977, the joint venture surveyed for patent claims on public domain that would be interior to a crack-line projected at 45 degrees from the bottom of the American Eagle deposit. This survey was filed with the BLM but the claims were not patented. Exxon ceased contributing to the joint venture in 1985 and withdrew in 1987.

When Newmont distributed Magma’s equity to Newmont’s shareholders in 1987, Newmont’s ownership interest in properties at Copper Creek was incorporated into Magma and Magma became an independent company. Magma’s management had little interest in exploration at Copper Creek; they reduced the size of the property package, but held the core property. Magma met requirement for assessment expenditure by drilling three holes. Redhawk has logs and drill core for these holes.

Arizona Mineral Technology (AMT) finalized an agreement to acquire the Copper Creek property from Magma in 1994. Between 1960 and 1995 when AMT became active at Copper Creek, more than 77 deep holes had been drilled there by major copper companies and large amounts of geological, geophysical, geochemical and other analytical data had been generated by them. These explorers were searching for a major porphyry copper deposit; the mineralized pipes were too small to interest these major companies.

AMT began field investigations at Copper Creek in the spring of 1995; the relatively shallow mineralized pipes were favored targets for AMT. Claims were staked to recover the ground dropped by Magma and to fill fractions. Agreements to acquire the Bell (Ryland) ranch and the Mercer ranch were signed. An agreement was signed with Phelps Dodge Exploration Corporation to obtain an interest in their patented claim block. AMT obtained a Prospecting Permit for State lands in the south half of Section 2, near the Bluebird mine. Access and drill roads were repaired and a new access road was constructed from Saloon Gulch to the top of White Bear hill. During May and June 1995, AMT drilled nine reverse circulation (RC) holes at Old Reliable to confirm that leaching by Ranchers had not significantly depleted the chalcocite ore body there. In addition, three RC holes were drilled at Old Reliable in June 1996 and 20 RC holes were drilled there in January through March 1997. Six of these vertical RC holes were extended with the core drill to test the deposit below the rubble column.

AMT drilled 40,135 feet in 37 angled diamond core holes to test the Childs Aldwinkle pipe above the 2800 elevation, in March through September, 1996. These westerly-directed holes were drilled from four surface sites, east of the Childs Aldwinkle glory-holes. In addition, 3,580 feet were drilled in nine RC holes to test the top of the blind north finger of the pipe and three vertical core holes were drilled to obtain metallurgical test samples. These holes, plus pre-AMT holes, comprise the data-base from which the resource in the Childs Aldwinkle pipe deposit has been estimated.

In the years 1976 through 1982, Newmont drilled two core holes beneath the south wall of Copper Creek canyon, almost directly beneath the prior location of the Arizona Molybdenum Corporation concentrator. Both of these holes cut mineralized intervals, of potential ore-grade. The near surface intercept in hole NE-10 was similar to other copper-mineralized breccia-pipe deposits in the area, but the deeper intercepts in hole NE-6 were pervasive sericite-chalcopyrite replacement of granodiorite. Follow-up holes drilled by AMT, 37,578 feet in 24 angled and seven vertical holes, defined the Mammoth breccia, a pipe-form, quartz-chalcopyrite veinlets stockwork deposit with N25W elongation; potentially economic parts of the pipe, bottom above the 2800 elevation. These 31 core holes drilled by AMT, plus Newmont’s hole NE-10, comprise the data-base from which the Mammoth pipe resource was estimated.

During November, 1996, hole VIX 28-2 extended through the relatively shallow Mammoth pipe and into sericite-chalcopyrite rock, similar to the deep mineral intercept in Newmont hole NE-6. The similarity between these mineral intercepts, about 700 feet apart, stimulated drilling of holes to test the continuity of the intervening “Lower Mammoth” (LM) mineralized zone. The Lower Mammoth deposit is a steep, N25W- trending, altered and mineralized sheared zone that clearly has fed mineralizing fluids upward, into the Mammoth pipe. In addition to Newmont’s hole NE-6, the Lower Mammoth zone has been tested by an additional 13 holes drilled by AMT; it is, however, incompletely drilled at this juncture. The limited current information indicates potentially economic parts of the Lower Mammoth feeder zone tops near 2400 elevation; it appears to have reasonable continuity for at least 700 feet along strike, to be open downward and to the southeast. Both tenor and thickness appear to increase toward the south, where thickness of the zone probably exceeds 100 feet. AMT mounted a staggered, 200-foot grid that covers much of the productive ground at Copper Creek. This grid was used to guide collection of geochemical samples, ground magnetic and radiometric surveys. The exploration survey data is in files controlled by Redhawk and warrants study. AMT exhausted its financial resources in 2001 and ceased all exploration. Norshield Investments, AMT’s primary creditor, advanced funds necessary to maintain the key properties at Copper Creek, but agreements to secure the “Ryland” ranch, the Mercer Ranch, the Phelps Dodge claims and Downey’s Moose claims were dropped.

Redhawk acquired AMT’s property at Copper Creek, as well as the drill core, rock samples and the accumulated project data, in 2005. Redhawk has subsequently organized and consolidated the available data and drill core. The historical core as well as core from subsequent drill proframs is now housed in a core storage facility in San Manuel, Arizona. San Manuel is 15 miles from Copper Creek and is where the project office for Redhawk Copper, Inc., a subsidiary of Redhawk Resources, Inc. is l;ocated. Redhawk continued to consolidate its property position in the district starting with the lease-purchase agreement in November 11, 2005 with D&G Mining Company for the four Moose unpatented claims. Early in 2007 Redhawk reached an agreement with Phelps Dodge Corporation (PD) to purchase 27 mineral claims (26 patented claims and one unpatented claim which is internal to the patented claims). The claims adjoin the patented claim groups owned by Redhawk on the northwest and are internal to Redhawk’s land holdings in the district. Starting in 2011 Redhawk staked an additional approximately 22 square miles of contiguous property to the Northwest of Copper Creek to maintain a secure district land position.

Mineral Resource

Copper Creek Historical Resource Estimate - Independent Mining Consultants June 25, 2012

Copper Creek Mineral resources historic estimate

An historical mineral resource estimate (the “Historical Estimate”) was published in a technical report titled “Copper Creek 2012 Mineral Resource Update, Pinal County, Arizona, USA, Technical Report” prepared for Redhawk by Independent Mining Consultants Inc., dated and filed by Redhawk on SEDAR on June 25, 2012. A qualified person (as defined in National Instrument 43-101 (“NI 43-101”)), has not done sufficient work to classify the foregoing historical estimate as current mineral resources or reserves, and CopperBank is not treating the estimate as current mineral resources or reserves. The Historical Estimate was calculated using a 0.20% copper equivalent (“CuEq”) cut-off grade. The Historical Estimate is based on metal prices of US$3.00/lb CuEq and contained within an open pit geometry using industry comparable estimates for direct mining, milling, and G&A costs. The ratios for calculating CuEq are based upon US$2.75/lb Cu, US$12.00/lb Mo, and US$20.00/oz Ag and recoveries of 90% for Cu, 80% for Mo, and 90% for Ag.

Because the Historical Estimate was completed relatively recently in 2012 and in compliance with the definitions for mineral resource categorization set out by the Canadian Institute of Mining, Metallurgy and Petroleum, and disclosed in a technical report conforming to the requirements of NI 43-101, CopperBank is of the view that the Historical Estimate is generally reliable and relevant to an evaluation of the property, however CopperBank has not completed any independent verification of the Historical Estimate. In order to verify the Historical Estimate as current, a qualified person (as defined in NI 43-101) would have to conduct a site visit on behalf of CopperBank and complete standard data verification procedures.  CopperBank intends to complete additional resource expansion drilling on Copper Creek for purposes of increasing and upgrading the mineral resource prior to completion of a new mineral resource estimate.  Totals may not add due to rounding.