IAMGOLD Updates Diamond Drilling Results on its Advanced Boto Exploration Project, Senegal

TORONTO, May 31, 2017 /PRNewswire/ - IAMGOLD Corporation ("IAMGOLD" or the "Company") today announced additional drilling results from its 100% owned Boto Gold Project in eastern Senegal, West Africa. The reported assay results are from the remaining twenty-two diamond drill holes, totaling 2,842 metres, completed at the Malikoundi deposit and Malikoundi North extension. The Company's ongoing drilling program had resumed in the fourth quarter of 2016 after seasonal rains, and continued into the first quarter of 2017.

The assay results are provided in Tables 1 and 2 and include the following highlights:

Malikoundi Deposit (Deepened Holes):

• Drill Hole DBDD-2201: 37 metres grading 1.83 g/t gold
  and 19 metres grading 3.28 g/t gold
  
  
• Drill Hole DBDD-2261: 42 metres grading 1.26 g/t gold
  
  
• Drill Hole DBDD-2266:77 metres grading 4.35 g/t gold
  Includes: 9 metres grading 11.76 g/t gold

Malikoundi North Extension:

• Drill Hole DBDD-2321: 14 metres grading 1.64 g/t gold
  
  
• Drill Hole DBDD-2322: 22 metres grading 1.79 g/t gold

Craig MacDougall, Senior Vice President, Exploration for IAMGOLD, stated, "With the last round of drilling results now in hand from our drilling program at the Malikoundi deposit, we are working to update the resource model for use in our ongoing technical evaluation of the project.  Our drilling activities are now focused on targeting possible resource expansions at the Boto 5 and Boto 6 deposits."

BOTO PROJECT, SENEGAL

The Boto project comprises 236 square kilometres of exploration licenses located in eastern Senegal along the Senegal-Mali border.  The geological setting of the project area is similar to the prolific Sadiola and Loulo gold districts in adjacent Mali, being underlain by highly prospective, Birimian-aged metasedimentary, volcanic and intrusive rocks along a seven-kilometre strike length of the Senegal-Mali Shear Zone.

As of December 31, 2016, the project hosts an indicated resource of 27.7 million tonnes averaging 1.8 grams of gold per tonne for 1.56 million ounces and an inferred resource of 2.9 million tonnes averaging 1.3 grams of gold per tonne for 125,000 ounces (see news release regarding reserves and resources dated February 22, 2017).

Next Steps

The drilling results from Malikoundi will be incorporated into an updated resource model for the Boto project.  Diamond drilling activities continue on the property targeting additional mineral resources along known mineralized trends associated with the Boto 5 and Boto 4-6 deposits.

Technical Information and Quality Control Notes

Boto Project, Senegal:

The Boto drilling results contained in this news release have been prepared in accordance with National Instrument 43-101 Standards of Disclosure for Mineral Projects. The sampling of, and assay data from, drill core is monitored through the implementation of a quality assurance - quality control (QA-QC) program designed to follow industry best practice. Drill core (HQ and NQ size) samples are selected by the IAMGOLD geologists and sawn in half with a diamond saw at the project site. Half of the core is retained at the site for reference purposes. Sample intervals are generally 1 metre in length. Samples are prepared at the Veritas Preparation Laboratory in Bamako, Mali and analyzed using a standard fire assay with a 50 gram charge with an Atomic Absorption (AA) finish at the Veritas Analytical Laboratory in Abidjan, Ivory Coast.

Qualified Persons

The information in this news release was prepared under the supervision of, and reviewed and verified by, Craig MacDougall, P.Geo., Senior Vice President, Exploration for IAMGOLD. Mr. MacDougall is a Qualified Person as defined by National Instrument 43-101.

Forward Looking Statement

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 (including, without limitation, statements regarding expected, estimated or planned gold production, cash costs, margin expansion, capital expenditures and exploration expenditures and statements regarding the estimation of mineral resources, exploration results, potential mineralization, potential mineral resources and mineral reserves) are forward-looking statements. Forward-looking statements are generally identifiable by use of the words "will", "continue", "expect", "estimate",  "intend", "to have', "plan" 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 of the Company 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, among other things, without limitation, failure to meet expected, estimated or planned gold production, cash costs, margin expansion, capital expenditures and exploration expenditures and failure to establish estimated mineral resources, 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 and Canadian provincial securities regulatory authorities. 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.

About IAMGOLD

IAMGOLD (www.iamgold.com) is a mid-tier mining company with four operating gold mines on three continents. A solid base of strategic assets in North and South America and West Africa is complemented by development and exploration projects and continued assessment of accretive acquisition opportunities. IAMGOLD is in a strong financial position with extensive management and operational expertise.

Please note:

This entire news release may be accessed via fax, e-mail, IAMGOLD's website at www.iamgold.com and through CNW Group's website at www.newswire.ca. All material information on IAMGOLD can be found at www.sedar.com or at www.sec.gov.

Si vous désirez obtenir la version française de ce communiqué, veuillez consulter le http://www.iamgold.com/French/accueil/default.aspx.

Boto Project Drillhole Map

SOURCE IAMGOLD Corporation