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.
We are seeking a highly organized and proactive Administrative Assistant to support day-to-day administrative operations across multiple locations. 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 calendar and travel coordination, expense management, on-site office support, and serve as backup to the Executive Assistant when needed. This position requires strong communication skills, flexibility, and the ability to manage competing priorities in a fast-paced environment.
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
On-Site & Office Support (Multiple Locations)
Provide in-office support across multiple sites 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
1–3 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
At Mariana Minerals, you’ll be part of a mission-driven team reshaping the way critical minerals are sourced and supplied globally. You’ll have the autonomy to make big decisions, the tools to innovate, and a culture that values ownership, smart automation, and collaboration.
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.
Mariana is an Equal Opportunity Employer. We celebrate diversity and are committed to creating an inclusive environment for all employees. We do not discriminate on the basis of race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, veteran status, or any other protected status.
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