[Form 4] CENTURY ALUMINUM CO Insider Trading Activity

Rhea-AI Filing Summary

Glencore entities reported Section 16 activity in Century Aluminum (CENX). On 09/30/2025 Glencore AG converted 28.48 shares of Series A Convertible Preferred Stock into 2,848 shares of Common Stock. The filing also reports a disposition of 27,500,000 shares of Common Stock. Following the reported transactions, the filing shows 12,557,356 shares beneficially owned on an indirect basis. The converted preferred shares are held by Glencore AG, which is a direct wholly-owned subsidiary of Glencore International AG; Glencore plc may be deemed an indirect owner of those holdings.

Positive

• Conversion disclosed of Series A Convertible Preferred Stock into common shares, increasing transparency
• Clear ownership chain showing holdings by Glencore AG, Glencore International AG and potential indirect ownership by Glencore plc

Negative

• Large reported disposition of 27,500,000 common shares without stated purpose or price
• Filing lacks transaction price details for the reported disposition, limiting assessment of economic impact

Insights

Financial Analyst

TL;DR: Large 27.5M-share disposition with a small preferred-to-common conversion; ownership structure consolidates control across Glencore entities.

The filing records a conversion of 28.48 Series A preferred shares into 2,848 common shares and a notable reported disposal of 27,500,000 common shares. The remaining reported beneficial ownership is 12,557,356 shares (indirect). For investors, the key facts are the sizeable direct disposal and the intercompany holdings: Glencore AG holds converted shares while Glencore International AG holds additional common stock, with Glencore plc as the ultimate parent. The filing provides transaction details but does not state prices or the purpose of the disposal.

Corporate Governance Expert

TL;DR: Related-party conversions and large disposition warrant attention to insider coordination and ownership concentration.

The report documents related Glencore entities acting as reporting persons, showing conversion mechanics for Series A Convertible Preferred Stock and a material disposal of common shares. The disclosure clarifies direct and indirect ownership chains but does not explain the rationale for the 27.5M-share disposition or whether it was part of a corporate reorganization. The filing is compliant in form and links holdings across Glencore AG, Glencore International AG and Glencore plc.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

GLENCORE INTERNATIONAL AG

(Last) (First) (Middle)

BAARERMATTSTRASSE 3

P.O. BOX 1363

(Street)

BAAR V8 CH-6341

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
CENTURY ALUMINUM CO [ CENX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
09/30/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	09/30/2025		C		2,848	A	(1)(2)	12,557,356	I	See Footnote(3)
Common Stock								27,500,000	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series A Convertible Preferred Stock	(2)	09/30/2025		C			28.48	(2)	(2)	Common Stock	2,848	(2)	49,485.91	I	See Footnote(3)

1. Name and Address of Reporting Person^*

GLENCORE INTERNATIONAL AG

(Last) (First) (Middle)

BAARERMATTSTRASSE 3

P.O. BOX 1363

(Street)

BAAR V8 CH-6341

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Glencore AG

(Last) (First) (Middle)

BAARERMATTSTRASSE 3

P.O. BOX 1363

(Street)

BAAR V8 CH-6341

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Glencore plc

(Last) (First) (Middle)

BAARERMATTSTRASSE 3

P.O. BOX 1363

(Street)

BAAR V8 CH-6341

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. Represents shares of Common Stock acquired upon conversion of 28.48 shares of Series A Convertible Preferred Stock on September 30, 2025.

2. Each share of Series A Convertible Preferred Stock is convertible into 100 shares of Common Stock at the times and under the circumstances described in the Certificate of Designation for the Series A Convertible Preferred Stock. The Series A Convertible Preferred Stock has no expiration date.

3. The shares of Common Stock reported in Line 1 of Table I and the shares of Series A Convertible Preferred Stock reported in Table II are held directly by Glencore AG, a direct wholly-owned subsidiary of Glencore International AG, and may be deemed to be indirectly beneficially owned by Glencore International AG. The Common Stock reported on Line 2 of Table I is held directly by Glencore International AG. Glencore International AG is wholly owned by Glencore plc, which may be deemed an indirect beneficial owner of the securities held by Glencore AG and Glencore International AG.

	GLENCORE INTERNATIONAL AG By: /s/ John Burton Name: John Burton Title: Director By: /s/ Steven Kalmin Name: Steven Kalmin Title: Director	10/02/2025
	GLENCORE AG By: /s/ Martin Haering Name: Martin Haering Title: Director By: /s/ Carlos Perezagua Name: Carlos Perezagua Title: Director	10/02/2025
	GLENCORE PLC By: /s/ John Burton Name: John Burton Title: Company Secretary	10/02/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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FAQ

What securities did Glencore report for CENX on the Form 4?

The filing reports conversion of 28.48 shares of Series A Convertible Preferred Stock into 2,848 common shares and a reported disposition of 27,500,000 common shares.

When did the reported transaction(s) occur for CENX?

The conversion and reported activity are dated 09/30/2025 in the Form 4.

How many CENX shares are reported as beneficially owned after the transactions?

The filing shows 12,557,356 shares beneficially owned following the reported transactions, on an indirect basis.

Which Glencore entities are listed as reporting persons on the Form 4?

The reporting persons are Glencore International AG, Glencore AG, and Glencore plc, with addresses in Baar, Switzerland.

Does the Form 4 explain why the 27,500,000 shares were disposed?

No. The filing lists the disposition amount but does not provide a purpose or price for the 27,500,000-share disposal.