The Natural Stone Institute (NSI) is the leading US trade association for the natural stone industry, and its sustainability program is anchored by the Natural Stone Sustainability Standard (ANSI/NSC 373) — an American National Standard that lets quarriers and fabricators earn certification for responsible production. For specifiers weighing natural stone against silica-free engineered surfaces, understanding what this standard does — and doesn’t do — matters more than ever.

What ANSI 373 Certifies

ANSI/NSC 373 covers environmental and social responsibility criteria for natural stone production, including land use, water, energy, waste, and community impact. Certification is awarded to quarries and fabrication facilities that meet the standard’s requirements, verified by third-party assessment. The standard is administered by NSF International with the Natural Stone Institute’s support.

• Quarry site management and restoration requirements
• Energy use and greenhouse gas reporting
• Water management and wastewater treatment
• Worker health, safety, and social responsibility criteria
• Chain of custody for certified product claims

How the Sustainability Conversation Has Shifted in 2025–2026

The last two years have pushed sustainability to the top of the surface-materials agenda in a way that catches both camps off guard:

• LEED v5 and similar green building systems are tightening credit requirements around EPDs and material transparency.
• EU regulatory pressure (CBAM, the revised Construction Products Regulation) is pulling carbon data into the mainstream of building product specification.
• Silica-free engineered brands are marketing recycled mineral content and verified low-carbon production as core value propositions, not side claims.
• Natural stone continues to argue a “low processing energy” case, but faces the same EPD data demands as everyone else.

What This Means for Your Next Project

If you’re specifying surfaces for a commercial or hospitality project, here’s a practical checklist:

1. Ask for the EPD — whether the product is natural stone, quartz, or silica-free engineered.
2. If natural stone is shortlisted, check whether the quarry holds ANSI 373 certification and what it covers.
3. If an engineered surface is shortlisted, ask whether the silica-free claim is backed by XRD testing and whether recycled content is documented.
4. Compare like with like: carbon per m², declared unit, and verification basis — not marketing language.

For a comparison of material options, see our Zero-Silica vs Low-Silica guide and our Resource Library.