IAMGOLD Releases High Grade Infill Drill Results at the Diakha-Siribaya Gold Project in Mali

Toronto, Ontario--(Newsfile Corp. - November 30, 2021) - IAMGOLD Corporation (TSX: IMG) (NYSE: IAG) ("IAMGOLD" or the "Company") is pleased to announce results from its 2021 exploration infill drilling program completed at the Diakha deposit on its wholly owned Diakha-Siribaya Gold project located in western Mali along the borders with Senegal and Guinea.

Highlights include:

Diamond Drill Holes (refer to Table 1 below)

• 12 meters ("m") at 9.32 grams per tonne gold ("g/t Au") in drill hole SRD21-284 from 284 m including
  • 3 m at 27.15 g/t Au from 284 m
• 13 m at 11.20 g/t Au in drill hole SRD21-303 from 277 m including
  • 2 m at 67.98 g/t Au from 279 m
• 10 m at 11.70 g/t Au in drill hole SRD21-305 from 164 m including
  • 4 m at 27.63 g/t Au from 169 m
• 17 m at 2.17 g/t Au in drill hole SRD21-300 from 177 m, followed by a separate interval of:
  • 20 m at 5.47 g/t Au from 269 m including
  • 7 m at 11.74 g/t Au from 282 m
• 20 m at 5.40 g/t Au in drill hole SRD21-308 from 108 m including
  • 1 m at 69.34 g/t Au from 114 m
• 13 m at 4.12 g/t Au in drill hole SRD21-307 from 224 m including
  • 1 m at 17.40 g/t Au from 225 m and
  • 2 m at 13.40 g/t Au from 233 m
• 15 m at 3.91 g/t Au in drill hole SRD21-311 from 242 m including
  • 3 m at 13.06 g/t Au from 246 m and
  • 1 m at 11.40 g/t Au from 251 m

Reverse Circulation ("RC") Drill Holes (refer to Table 2 below)

• 16 m at 14.00 g/t Au in drill hole SRD21-891 from 89 m including
  • 3 m at 41.95 g/t Au from 99 m
• 20 m at 1.97 g/t Au in drill hole SRD21-883 from 43 m, including
  • 1 m at 21.89 g/t Au from 48 m, followed by a separate interval of:
  • 27 m at 2.12 g/t Au from 75 m including
  • 3 m at 6.52 g/t Au from 76 m and
  • 1m at 21.31 g/t Au from 101 m
• 12 m at 4.19 g/t Au in drill hole SRD21-889 from 108 m including
  • 2 m at 18.84 g/t Au from 117 m
• 32 m at 1.97 g/t Au in drill hole SRD21-907 from 88 m including
  • 1 m at 16.40 g/t Au from 89 m
• 11 m at 4.96 g/t Au in drill hole SRD21-848 from 55 m including
  • 1 m at 39.80 g/t Au from 65 m
• 24 m at 2.23 g/t Au in drill hole SRD21-882 from 43 m including
  • 2 m at 17.01 g/t Au from 54 m

Craig MacDougall, Executive Vice President, Growth for IAMGOLD, stated: "We are very pleased with the results of our 2021 exploration program, which have helped to demonstrate continuity of mineralization between previously completed drill holes and better delineate the distribution and controls on high grade mineralized structures within the known resource."

"The data from this program will help improve the current deposit model and support the completion of an updated mineral resources estimation as we continue to advance towards our objective of increasing total indicated resources to above 1.5 million ounces."

In 2021, the Company completed a combined 19,952 meters in 131 diamond and RC drill holes with 22,328 assay samples (including QA/QC samples) submitted for analysis. The main objective of the drilling program was to infill and increase confidence in the current resources estimate for the Diakha deposit.

Diakha-Siribaya Gold Project

The Diakha-Siribaya project is wholly-owned by IAMGOLD and consists of eight contiguous exploration permits which cover a total area of 596.5 square kilometres, located in the Kédougou-Kéniéba inlier of the West African Craton region of western Mali along the borders with Senegal and Guinea.

Gold mineralization is hosted within highly prospective, Birimian-aged metasedimentary, volcanic and intrusive rocks proximal to the Senegal-Mali Shear Zone. At Diakha, the largest deposit discovered to date, gold mineralization occurs within an albitized sandstone unit similar to that hosting IAMGOLD's Boto Gold deposit located approximately 10 kilometres to the north along strike.

The current mineral resources estimate for the Diakha deposit (on a 100% basis using a $1,500 per ounce gold price) comprises 15.9 million tonnes of indicated resources averaging 1.20 grams of gold per tonne for 615,300 ounces of gold and 18.2 million tonnes of inferred resources averaging 1.62 grams of gold per tonne for 947,500 ounces (see news releases dated January 30, 2019 and February 17, 2021).

Next Steps

The drilling data from the 2021 exploration program is currently being incorporated into a revised deposit model to support the completion of an updated mineral resources estimate targeted for completion in the first half of 2022.

Figure 1 - Diakha-Siribaya - Diakha deposit drill hole surface plan and highlighted 2021 assays

To view an enhanced version of Figure 1, please visit:
https://orders.newsfilecorp.com/files/6077/105661_219a68a1247b3952_001full.jpg

Figure 2 - Diakha-Siribaya - Diakha deposit longitudinal section and highlighted 2021 assay results

To view an enhanced version of Figure 2, please visit:
https://orders.newsfilecorp.com/files/6077/105661_219a68a1247b3952_002full.jpg

Notes:

1. The true widths of intersections are unknown at this time, but are interpreted to approximate the reported downhole lengths.
2. Drillhole intercepts are calculated using a minimum downhole length of two (2) meters, a cut-off grade of 0.5 g/t gold, and may include up to four (4) metres of internal dilution.
3. Assays are reported uncut, but high grade sub-intervals are highlighted.

Notes:

1. The true widths of intersections are unknown at this time, but are interpreted to approximate the reported downhole lengths.
2. Drillhole intercepts are calculated using a minimum downhole length of two (2) meters, a cut-off grade of 0.5 g/t gold, and may include up to four (4) metres of internal dilution.
3. Assays are reported uncut, but high grade sub-intervals are highlighted.

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING INFORMATION

This news release contains forward-looking statements. All statements, other than of historical fact, that address activities, events or developments that the Company believes, expects or anticipates will or may occur in the future are forward-looking statements. Forward-looking statements are generally identifiable by, but not limited to, the use of the words "may", "will", "should", "would", "continue", "expect", "expected", "budget", "forecast", "anticipate", "estimate", "believe", "intend", "appear" "plan", "schedule", "guidance", "outlook", "potential", "plans", "targeted", "focused", or "project" or the negative of these words or other variations on these words or comparable terminology. Forward-looking statements are subject to a number of risks and uncertainties, many of which are beyond the Company's ability to control or predict, that may cause the actual results to differ materially from those discussed in the forward-looking statements. Factors that could cause actual results or events to differ materially from current expectations include, but are not limited to, differences in the mineral content within the material identified as mineral resources or mineral reserves from that predicted, the failure to accurately estimate mineral resources or mineral reserves, unexpected increases in capital expenditures, operating expenditures and exploration expenditures, changes in development or mining plans due to changes in logistical, technical or other factors, the possibility that future exploration results will not be consistent with the Company's expectations, changes in world gold markets and other risks disclosed in IAMGOLD's most recent Form 40-F/Annual Information Form on file with the United States Securities and Exchange Commission at www.sec.gov/edgar.shtml and Canadian securities regulatory authorities at www.sedar.com, which are incorporated herein. Any forward-looking statement speaks only as of the date on which it is made and, except as may be required by applicable securities laws, the Company disclaims any intent or obligation to update any forward-looking statement. The Company disclaims any intention or obligation to update or revise any forward-looking statements whether as a result of new information, future events or otherwise except as required by applicable law.

CAUTIONARY NOTE TO U.S. INVESTORS REGARDING DISCLOSURE OF MINERAL RESERVE AND MINERAL RESOURCE ESTIMATES

The mineral resource and reserve estimates contained in this news release have been prepared in accordance with NI 43-101. These standards are similar to those used by the United States Securities and Exchange Commission (the "SEC") Industry Guide No. 7, as interpreted by the SEC staff. However, the definitions in NI 43-101 differ in certain respects from those under Industry Guide 7. Accordingly, mineral resource and reserve information contained in this news release may not be comparable to similar information disclosed by United States companies. Under the SEC's Industry Guide 7, mineralization may not be classified as a "reserve" unless the determination has been made that the mineralization could be economically and legally produced or extracted at the time the reserve determination is made.

As a result of the adoption of amendments to the SEC's disclosure rules (the "SEC Modernization Rules"), which more closely align its disclosure requirements and policies for mining properties with current industry and global regulatory practices and standards, including NI 43-101, and which became effective on February 25, 2019, the SEC now recognizes estimates of "measured mineral resources", "indicated mineral resources" and "inferred mineral resources." In addition, the SEC has amended definitions of "proven mineral reserves" and "probable mineral reserves" in its amended rules, with definitions that are substantially similar to those used in NI 43-101. Issuers must begin to comply with the SEC Modernization Rules in their first fiscal year beginning on or after January 1, 2021, though Canadian issuers that report in the United States using the Multijurisdictional Disclosure System ("MJDS") may still use NI 43-101 rather than the SEC Modernization Rules when using the SEC's MJDS registration statement and annual report forms.

United States investors are cautioned that while the SEC now recognizes "measured mineral resources", "indicated mineral resources" and "inferred mineral resources" under the SEC Modernization Rules, investors should not assume that any part or all of the mineral deposits in these categories will ever be converted into a higher category of mineral resources or into mineral reserves. These terms have a great amount of uncertainty as to their economic and legal feasibility. Under Canadian regulations, estimates of inferred mineral resources may not form the basis of feasibility or pre-feasibility studies, except in limited circumstances.

Investors are cautioned not to assume that any "measured mineral resources", "indicated mineral resources", or "inferred mineral resources" that the Company reports in this news release are or will be economically or legally mineable. Further, "inferred mineral resources" have a great amount of uncertainty as to their existence and as to their economic and legal feasibility. It cannot be assumed that any part or all of an inferred mineral resource will ever be upgraded to a higher category.

QUALIFIED PERSONS, TECHNICAL INFORMATION AND QUALITY CONTROL NOTES

The drilling results contained in this news release have been prepared in accordance with National Instrument 43-101 Standards of Disclosure for Mineral Projects ("NI 43-101").

Philippe Biron, P. Geo., Regional Senior Geologist, West Africa for IAMGOLD responsible for the supervision of the preparation, verification and review of the technical information in this release. Mr. Biron is a "qualified person" (a "QP") for the purposes of NI 43-101 with respect to the technical information being reported on in this release.

The information in this news release was reviewed and approved by Craig MacDougall, P.Geo., Executive Vice President, Growth for IAMGOLD. Mr. MacDougall is a QP for the purposes of NI 43-101. The technical information has been included herein with the consent and prior review of the above noted QPs.

The sampling of, and assay data from, drill core and RC chips are monitored through the implementation of a quality assurance/quality control program designed to follow industry best practice. Rock chips from RC drilling are collected at the rig site, at one meter intervals, under the direct supervision of IAMGOLD geologists and field technicians. Samples are riffle split to obtain two 3 kilogram samples. One sample is retained for reference purposes and the other is sent for assay. Drill core (HQ and NQ size) samples were selected by the IAMGOLD geologists and sawn in half with a diamond saw at the project site, drill core sample intervals are systematically one meter in length. Half of the core is retained at the site for reference purposes, while the other half is sent to the laboratory for prep and analysis.

The samples were assayed at the SGS Minerals Analytical Laboratory in Bamako, Mali, using a standard fire assay with a 50-gram charge and an Atomic Absorption finish (FAA505). All samples returning values greater than 10.0 grams per tonne of gold were re-assayed using a gravimetric finish (FAG505).

About IAMGOLD

IAMGOLD is a mid-tier gold mining company operating in three regions globally: North America, South America and West Africa. Within these regions the Company is developing high potential mining districts that encompass operating mines and construction, development and exploration projects. The Company's operating mines include Essakane in Burkina Faso, Rosebel (including Saramacca) in Suriname and Westwood in Canada. A solid base of strategic assets is complemented by the Côté Gold construction project in Canada, the Boto Gold development project in Senegal, as well as greenfield and brownfield exploration projects in various countries located in the Americas and West Africa.

IAMGOLD employs approximately 5,000 people. IAMGOLD is committed to maintaining its culture of accountable mining through high standards of Environmental, Social and Governance practices, including its commitment to Zero Harm®, in every aspect of its business. IAMGOLD (www.iamgold.com) is listed on the New York Stock Exchange (NYSE: IAG) and the Toronto Stock Exchange (TSX: IMG) and is one of the companies on the JSI index¹.

1 Jantzi Social Index ("JSI"). The JSI is a socially screened market capitalization-weighted common stock index modeled on the S&P/TSX 60. It consists of companies which pass a set of broadly based environmental, social and governance rating criteria.

IAMGOLD Contact Information

Graeme Jennings, Vice President, Investor Relations
Tel: 416 360 4743 | Mobile: 416 388 6883

Philip Rabenok, Manager, Investor Relations
Tel: 416 933 5783 | Mobile: 647 967 9942

Toll-free: 1 888 464 9999
info@iamgold.com

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