About this role
About Mariana MineralsMariana 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 RoleWe are seeking a highly organized and proactive Administrative Assistant to support day-to-day administrative operations at our Houston office. 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.
The Administrative Assistant will provide administrative 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.
What You’ll DoAdministrative & 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
On-Site & Office Support
Provide in-office support as needed
Coordinate office supplies, deliveries, and facilities-related requests
Assist with visitor management and on-site meeting logistics
Support internal events and team off-sites
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 Qualifications1–3+ years of administrative 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!