v3.26.1
Financial risk management (Tables)
 12 Months Ended
Dec. 31, 2025
Notes and other explanatory information [abstract]  
Schedule of sensitivity analysis risk factors affecting price of financial instrument
                         
        Impacts on income statement   Impacts on statement of comprehensive income
        Scenarios II and III   Scenarios II and III
Risk factor Quotation at December 31, 2025 Amount   Changes from 2025 Scenario I -25% -50% +25% +50%   Scenario I -25% -50% +25% +50%
Cash and cash equivalents and financial investments                          
Foreign exchange rates                           
USD  5,5024 12,513   (1.20%)  (150)     (3,128) (6,256) 3,128 6,256    -     -     -     -     -   
EUR  6,4692 4,856   (0.42%)  (20)     (1,214)       (2,428)        1,214        2,428    -     -     -     -     -   
PEN  1,6365        51,177   (4.75%)         (2,429)   (12,794)     (25,588)      12,794      25,588    -     -     -     -     -   
Interest rates                              
BRL - CDI - SELIC 14.90% 134,737   (72,92) bps  (983)     (5,019)     (10,038)        5,019      10,038    -     -     -     -     -   
                               
Loans and financings                              
Foreign exchange rates                              
USD  5,5024 180,080   (1.20%) 2,161     45,020      90,040  (45,020)     (90,040)    -     -     -     -     -   
Interest rates                              
BRL - CDI - SELIC 14.90% 130,157   (72,92) bps 949       4,848        9,697  (4,848)       (9,697)    -     -     -     -     -   
USD - SOFR 3.64% 180,080   (27) bps 488       1,638        3,275  (1,638)       (3,275)    -     -     -     -     -   
IPCA - TLP 4.26% 166,364   6 bps  (102)       1,772        3,544  (1,772)       (3,544)    -     -     -     -     -   
BRL - TJLP 9.07% 18,047   11 bps  (20)         409           818         (409)         (818)    -     -     -     -     -   
                               
Other financial instruments                            
Foreign exchange rates                              
USD  5,5024 750,000   (1.20%) 1,559     42,818    128,453  (25,691)     (42,818)    -     -     -     -     -   
Interest rates                              
BRL - CDI - SELIC 14.90% 750,000   (72,92) bps 108         570        1,199         (519)         (992)    -     -     -     -     -   
USD - SOFR 3.64% 870,943   27 bps 23         113           226         (113)         (225)    9  99  199  (97)  (194)
Dollar coupon 4.81% 650,000   (41) bps  (2,617)     30,324      60,649  (30,324)     (60,649)    -     -     -     -     -   
Commodities price                              
Zinc 3,063.50 743,061   (6.97%) 9,676     27,379      54,757  (27,378)     (54,757)    (3,880) (10,978) (21,957)  10,978  21,957
Gold 4,337.88 8,968   (12.98%) -             - -              - -   628  1,506  3,716  2     (3,473)
Silver 71,99 118,914   (41.66%) - -      - -     -    24,057  13,506 33,436  (15,857) (37,075)
Schedule of foreign exchange effects
       
USD amounts of foreign currency balances   2025   2024
Assets        
Cash, cash equivalents and financial investments     125,345     98,067
Other financial instruments     28,243     70
Trade accounts receivables     20,946     19,553
Total Assets     174,534   117,690
Liabilities        
Loans and financings     312,115     297,199
Other financial instruments     21,021     238
Trade payables     205,414     162,288
Confirming payables     102,252     28,518
Lease liabilities     44,184     42,357
Use of public assets     18,808     18,047
Total Liabilities     703,794     548,647
         
Net exposure     (529,260)     (430,957)
Schedule of credit quality of financial assets
                       
            2025           2024
    Local rating   Global rating   Total   Local rating   Global rating   Total
Cash and cash equivalents                    
AAA   64,464   -   64,464   251,962   -   251,962
AA+   1   -   1   1   -   1
AA   -   57,071   57,071   -   95,461   95,461
AA-   -   32,544   32,544   -   18,714   18,714
A+   -   172,533   172,533   -   127,151   127,151
A   -   331   331   8,265   24,749   33,014
A-   -   29,923   29,923   -   61,935   61,935
BBB+   -   58,527   58,527   -   -   -
BBB   -   52,290   52,290   -   -   -
No rating (i)   48,186   1   48,187   11,899   20,400   32,299
    112,651   403,220   515,871   272,127   348,410   620,537
            2025           2024
    Local rating   Global rating   Total   Local rating   Global rating   Total
Financial investments                    
AAA   5,608   -   5,608   19,638   -   19,638
No rating (i)   79   -   79   55   -   55
    5,687   -   5,687   19,693   -   19,693
Derivative financial instruments                    
AAA   2,089   -   2,089   71   -   71
AA   -   4,421   4,421   -   -   -
A+   -   2,014   2,014   -   450   450
A   -   -   -   -   842   842
A-   -   28,243   28,243   -   3,919   3,919
    2,089   34,678   36,767   71   5,211   5,282
Other assets                        
AAA   1,080   -   1,080   883   -   883
    1,080   -   1,080   883   -   883

(i) Refers to subsidiaries of international financial institutions that do not have a global rating available in the international rating agencies. According to the Company's policy, for these financial institutions, the rating of the financial institution controlling entities is assumed, which must be at least BBB-.
Schedule of liquidity risk
         
2025 Less than Between Between Over 5 years Total
1 year 1 and 3 years 3 and 5 years
Loans and financings 153,014 478,025 433,708 1,581,443 2,646,190
Lease liabilities 54,233 60,421 9,980 17,354 141,988
Derivative financial instruments 11,646 91 20,600 - 32,337
Trade payables 500,025 - - - 500,025
Confirming payables 415,388 - - - 415,388
Salaries and payroll charges 83,597 - - - 83,597
Dividends payable 26,918 - - - 26,918
Related parties - 4,695 - - 4,695
Asset retirement and environmental obligations 39,326 51,641 118,247 376,092 585,306
Use of public assets 3,331 3,542 3,992 27,499 38,364
  1,287,478 598,415 586,527 2,002,388 4,474,808

 

2024 Less than Between Between Over 5 years Total
1 year 1 and 3 years 3 and 5 years
Loans and financings 148,077 150,023 1,175,144 1,028,440 2,501,684
Lease liabilities 29,882 37,755 6,121 12,299 86,057
Derivative financial instruments 3,600 181 17 - 3,798
Trade payables 443,288 - - - 443,288
Confirming payables 268,175 - - - 268,175
Salaries and payroll charges 70,234 - - - 70,234
Dividends payable 3,707 - - - 3,707
Related parties 1,125 2,960 - - 4,085
Asset retirement and environmental obligations 47,937 76,583 60,598 364,036 549,154
Use of public assets 1,457 3,180 3,585 28,226 36,448
    1,017,482   270,682   1,245,465   1,433,001   3,966,630
Schedule of leverage ratio
           
  Note 2025   2024   2023
Loans and financings 24 (a)   1,705,984     1,762,633     1,725,566
Derivative financial instruments 16 (a)   (2,341)     (1,484)     2,600
Lease liabilities 23 (b)   121,134     95,899     77,405
Cash and cash equivalents 15 (a)   (515,871)     (620,537)     (457,259)
Financial investments   (5,687)   (19,693)   (11,058)
Net debt (i)     1,303,219     1,216,818     1,337,254
             
Net income (loss) for the year     223,144     (187,407)     (291,810)
Plus (less):            
 Depreciation and amortization 7   288,996     330,198     310,475
 Share in the results of associates     (21,143)     (21,223)     (23,536)
 Net financial results 10   187,365     369,460     167,058
 Income tax expense (benefit) 11 (a)   108,605     115,556     (4,274)
 Miscellaneous adjustments 2 (15,088)     107,496     248,128
Adjusted EBITDA (ii)     771,879     714,080     406,041
             
Leverage ratio (Net debt/Adjusted EBITDA)     1.68     1.70     3.29

(i) Net debt is defined as (a) loans and financings, plus lease liabilities, plus or minus (b) the fair value of derivative financial instruments, less (c) cash and cash equivalents, less (d) financial investments.

(ii) Adjusted EBITDA for capital management calculation uses the same assumptions described in note 2 for Adjusted EBITDA by segment.