As of May 04, 2026, the three largest insider holders of MTX are Douglas T Dietrich (Chairman And Ceo, 175.97K shares), Douglas T Dietrich (Chairman And Ceo, 161.68K shares), Dj Iii Monagle (Group President, 89.07K shares).
| Holder | Position | Shares (Direct) | Shares (Indirect) | Report Date |
|---|---|---|---|---|
| Douglas T Dietrich | Chairman And Ceo | 175,973 | 0 | 27 Jan, 2026 |
| Douglas T Dietrich | Chairman And Ceo | 161,675 | 0 | 01 May, 2025 |
| Dj Iii Monagle | Group President | 89,073 | 0 | 27 Jan, 2026 |
| Thomas J Meek | Senior Vice President | 83,852 | 0 | 05 Dec, 2022 |
| Jonathan J Hastings | Senior Vice President | 63,811 | 0 | 27 Jan, 2026 |
| Douglas W Mayger | Senior Vice President | 45,744 | 0 | 27 Jan, 2023 |
| Michael Cipolla | Vice President | 39,529 | 0 | 27 Jan, 2026 |
| Brett Argirakis | Group President | 32,600 | 0 | 27 Jan, 2026 |
| Matthew E Garth | Svp, Finance Treasury, Cfo | 13,591 | 0 | 08 Mar, 2022 |
| Matthew E Garth | Svp, Finance Treasury, Cfo | 13,491 | 0 | 28 Jan, 2022 |
| Erin Cutler | Vp, Human Resources | 7,734 | 0 | 27 Jan, 2026 |
| Timothy Jordan | Vice President | 7,279 | 0 | 27 Jan, 2026 |
| Erik Aldag | Svp Finance And Treasury, Cfo | 6,959 | 0 | 27 Jan, 2026 |
| Erik Aldag | Svp Finance And Treasury, Cfo | 4,245 | 0 | 01 May, 2025 |
| Kristina M Johnson | - | 1,400 | 0 | 05 May, 2025 |
| Rocky Motwani | - | 1,192 | 0 | 17 Jun, 2025 |
* Please note that the shares above only reflect shares from the fund portfolio and the institutional portfolio. Shares from the personal portfolio are excluded from this Institutional Ownership Page. See these insiders' latest transactions here on Insider Page.
| Transaction Date | Insider Name | Security Class | Transaction Type | Shares Traded | Price | Shares Remaining | Ownership | Code |
|---|---|---|---|---|---|---|---|---|
| 01 Apr, 2026 | Franklin Feder | PHANTOM STOCK UNITS | A | 239 | $0.00 | 23,223 | D | A |
| 01 Apr, 2026 | Carolyn K Pittman | PHANTOM STOCK UNITS | A | 102 | $0.00 | 18,711 | D | A |
| 06 Mar, 2026 | Rocky Motwani | PHANTOM STOCK UNITS | A | 11 | $0.00 | 6,185 | D | A |
| 06 Mar, 2026 | Joseph C. Breunig | PHANTOM STOCK UNITS | A | 35 | $0.00 | 19,622 | D | A |
| 06 Mar, 2026 | Robert L Clark | PHANTOM STOCK UNITS | A | 56 | $0.00 | 31,742 | D | A |
| 06 Mar, 2026 | Alison Ann Deans | PHANTOM STOCK UNITS | A | 27 | $0.00 | 15,439 | D | A |
| 06 Mar, 2026 | Franklin Feder | PHANTOM STOCK UNITS | A | 41 | $0.00 | 22,984 | D | A |
| 06 Mar, 2026 | Marc E Robinson | PHANTOM STOCK UNITS | A | 44 | $0.00 | 24,965 | D | A |
| 06 Mar, 2026 | John J Carmola | PHANTOM STOCK UNITS | A | 46 | $0.00 | 26,004 | D | A |
| 06 Mar, 2026 | Carolyn K Pittman | PHANTOM STOCK UNITS | A | 33 | $0.00 | 18,609 | D | A |
| 06 Mar, 2026 | Kristina M Johnson | PHANTOM STOCK UNITS | A | 7 | $0.00 | 4,081 | D | A |
| 23 Jan, 2026 | Dj Iii Monagle | Common Stock | A | 3,795 | $0.00 | 89,600 | D | M |
| 23 Jan, 2026 | Douglas T Dietrich | Common Stock | A | 11,016 | $0.00 | 177,094 | D | M |
| 23 Jan, 2026 | Erik Aldag | Common Stock | A | 2,243 | $0.00 | 7,377 | D | M |
| 23 Jan, 2026 | Timothy Jordan | Common Stock | A | 2,046 | $0.00 | 7,401 | D | M |
| 23 Jan, 2026 | Erin Cutler | Common Stock | A | 1,276 | $0.00 | 7,667 | D | M |
| 23 Jan, 2026 | Michael Cipolla | Common Stock | A | 1,427 | $0.00 | 39,671 | D | M |
| 23 Jan, 2026 | Brett Argirakis | Common Stock | A | 3,247 | $0.00 | 32,504 | D | M |
| 23 Jan, 2026 | Jonathan J Hastings | Common Stock | A | 3,113 | $0.00 | 63,441 | D | M |
| 23 Jan, 2026 | Dj Iii Monagle | Common Stock | D | 2,099 | $68.77 | 87,501 | D | F |