Administrative Assistant

Warmada; Houston (TX); On-site; USD 45,000 - 65,000; Full time

Job summary

Mariana Minerals is seeking an Administrative Assistant to provide executive support to the CFO, manage calendars and travel, and handle expense reporting. The role also supports day-to-day office operations and backs up the Executive Assistant during absences.

Ideal for someone early in their career who is detail-oriented, resourceful, and eager to grow within an operations or executive support function. Join a software-driven minerals company focused on responsible sourcing and growth, working

Qualifications

• 1–3+ years of administrative / executive or office support experience preferred.
• Strong organizational skills and attention to detail.
• Excellent written and verbal communication skills.
• Proficiency in Microsoft Office.
• Experience with expense management and calendar systems preferred.
• Ability to handle confidential information with discretion.
• Strong time management and prioritization skills.
• Problem-solving mindset.
• Professional and service-oriented approach.
• Adaptability in a fast-paced environment.
• Team player with a positive attitude.

Responsibilities

• Administrative & Calendar Support: schedule meetings, manage calendars, coordinate appointments.
• Prepare meeting materials, agendas, and notes as needed.
• Coordinate cross-functional meetings and company events.
• Travel & Logistics: book and manage domestic and international travel.
• Handle last-minute travel changes and troubleshoot logistics.
• Expense & Reporting Support: prepare and submit expense reports and reconcile receipts.
• Executive Assistant Backup: provide backup during absences and assist with ad hoc requests.

Job description

ABOUT MARIANA MINERALS

Mariana Minerals is a software-first, vertically integrated minerals company on a mission to supply the critical minerals powering modern energy, AI, and defense technologies. We’re reimagining the minerals supply chain by combining deep industry expertise with advanced software, automation, and data-driven decision-making.

THE ROLE

The Administrative Assistant will provide administrative / executive support to the CFO, including calendar and travel coordination and expense management, while also supporting day-to-day office operations. The role will also serve as backup to the Executive Assistant as needed. This position requires strong communication skills, flexibility, sound judgment, and the ability to manage competing priorities in a fast-paced environment. This role is ideal for someone early in their career who is detail-oriented, resourceful, and eager to grow within an operations or executive support function.

WHAT YOU’LL DO

Administrative & Calendar Support

• Assist with scheduling meetings, managing calendars, and coordinating internal and external appointments
• Help prepare meeting materials, agendas, and notes as needed
• Support coordination of cross-functional meetings and company events

Travel & Logistics

• Book and manage domestic and international travel (flights, hotels, ground transportation)
• Handle last-minute travel changes and troubleshoot logistical issues

Expense & Reporting Support

• Prepare and submit expense reports in a timely and accurate manner
• Reconcile receipts and assist with tracking budgets or spending reports

Executive Assistant Backup

• Serve as backup to the Executive Assistant during absences
• Provide overflow support during high-volume periods
• Assist with special projects and ad hoc requests

DESIRED QUALIFICATIONS

• 1–3+ years of administrative / executive or office support experience preferred
• Strong organizational skills and attention to detail
• Excellent written and verbal communication skills
• Proficiency in Microsoft Office
• Experience with expense management and calendar systems preferred
• Ability to handle confidential information with discretion
• Strong time management and prioritization skills
• Problem-solving mindset
• Professional and service-oriented approach
• Adaptability in a fast-paced environment
• Team player with a positive attitude

OUR CULTURE IS BUILT ON FOUR PRINCIPLES

• Everyone Gets Home Safe. We never put speed or cost ahead of people.
• Extreme Ownership. We take full responsibility for outcomes, relentlessly driving toward solutions.
• Engineer Out Requirements, then Automate. We simplify, optimize, and then automate for scale.
• Share Your Legos. We collaborate openly, share knowledge, and empower each other to build bigger, better solutions.

Join us as we build the future of responsible mineral sourcing and supply!