Aggregate is what makes a terrazzo floor look like terrazzo. The matrix is essentially the background; the aggregate is the design. This guide covers what's available, what works in which matrix, and how to think about sizing and sourcing.
Marble — the default
Marble has been the primary terrazzo aggregate for 2,000+ years because it grinds and polishes well, has predictable color stability, and exists in essentially every color that terrazzo designers want. Standard color families:
| Family | Examples | Notes |
|---|---|---|
| White / cream | Bianco Carrara, Thassos, Bianco Sivec | Workhorse — present in most blends |
| Black | Nero Marquina, Belgian Black | Strong contrast accent; can dull faster than harder marbles |
| Green | Verde Alpi, Verde Guatemala, Verde India | Veined chips produce lively floors |
| Red / pink | Rosso Verona, Rosa Portogallo, Tennessee Pink | Tennessee Pink is domestic, lower cost |
| Yellow / gold | Giallo Siena, Crema Marfil | Used sparingly for warmth |
| Grey / charcoal | Bardiglio, Pietra Serena | Subtle workhorse for institutional palettes |
Most floors use a blend of 2–5 marble varieties. The lab sample stage is where ratios get tuned — a blend that looks right at 60/30/10 will often need to shift to 50/35/15 once it's actually ground and polished, because the visible contribution of a color depends on aggregate density and grinding depth, not just percent by volume.
Recycled glass
Post-consumer recycled glass earns LEED MR credits and produces brighter, more saturated colors than marble can. Most glass aggregate comes from container-glass recycling (bottles, jars) and is processed into terrazzo sizes.
- Color range: cobalt blue, emerald green, amber, clear/crystal, mirror, and dichroic accents.
- Common content: 30–80% post-consumer per ASTM standards; verify against LEED requirements.
- Best in epoxy matrix — high pH cementitious matrix can etch some glass formulations.
- Size availability: #0–#3 standard; larger sizes typically by special order.
- Premium options: mirrored chips, iridescent glass, dichroic glass for accent percentage.
Granite
Granite aggregate is harder than marble and more abrasion-resistant, but the color palette is narrower (greys, blacks, dark reds, dark browns). It's the right choice for high-abrasion fields — transit-station concourses, warehouse circulation, museum-entry vestibules where carts and snow-melt grit hit the floor daily. The trade-off is that granite holds its color less brightly than marble; the floor reads more muted.
Mother-of-pearl and shell
Mother-of-pearl is the accent aggregate — never the base. Iridescent shell fragments scattered at 1–3% of the aggregate blend produce a low-level sparkle that reads under direct lighting. Cost per pound is high (typically 30–60× marble) but the volume is small, so the total cost adder is modest. Used in lobbies, hospitality, retail flagship floors.
Metal chips
Brass, aluminum, copper, and stainless-steel chips can be added to epoxy terrazzo at small percentages (1–3%) for accent. They polish flush with the surrounding aggregate and produce a metallic flicker under light. Aluminum and copper will oxidize and color-shift over time; brass and stainless hold their color.
Aggregate sizing
Size has as much visual impact as color. NTMA sizing conventions:
| Size | Approx. dimension | Visual character |
|---|---|---|
| #0 | 1/16"–1/8" | Subtle, fine-grained, reads almost solid |
| #1 | 1/8"–1/4" | Light pattern, suitable for tight residential |
| #2 | 1/4"–3/8" | Standard commercial — most visible aggregate |
| #3 | 3/8"–1/2" | Bold, statement-floor |
| #4 | 1/2"–5/8" | Maximum visibility; cementitious systems only |
| Venetian (jumbo) | 5/8"+ | Up to 1"+; large-scale historic and contemporary feature floors |
Epoxy systems are limited to #2 maximum because of the 3/8" total system thickness. Cementitious systems allow #4 in bonded and monolithic, and full Venetian sizes in sand-cushion (2-1/2" thickness).
Sourcing and lead time
- Domestic marble (Tennessee Pink, Vermont Verde Antique, Georgia White): 2–4 weeks.
- Italian and European marble: 4–8 weeks for standard, up to 12 weeks for custom blends.
- Recycled glass: 2–4 weeks from US suppliers; verify post-consumer content per LEED.
- Pre-blended NTMA mixes: 1–2 weeks from regional terrazzo suppliers.
- Custom blends or unusual specialty aggregate: include 2-week buffer for sample approval before bulk order.
Pre-blending at the supplier is usually the right move. The mix arrives at the jobsite as one bag, color-consistent across the entire pour. Field-blending from multiple bags can produce visible bag-to-bag variation in the finished floor.
Sample and approval process
- Designer specifies preliminary blend by ratio and aggregate sizes.
- Installer produces three 8"×8" lab samples at the proposed blend and adjacent variants.
- Designer and owner review samples under the project's actual lighting (overhead LED reads differently from showroom halogen).
- Blend is locked. Field mock-up is poured at 4'×4' for final approval under construction lighting.
- Approved mock-up becomes the standard against which production pours are judged.
Frequently asked
Can we use locally sourced aggregate for sustainability credit?
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Yes for LEED Regional Materials. Tennessee, Vermont, Georgia, and several Texas quarries produce terrazzo-grade marble that qualifies for projects within 500 miles. Aggregate is heavy — transportation is a meaningful share of embodied carbon.
Does aggregate choice affect slip resistance?
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Slightly. Larger aggregate creates a microscopically rougher surface and tends to read 0.02–0.05 higher on wet DCOF than fine-aggregate floors. Both fall well above the ANSI A326.3 threshold for level interior floors when properly finished.
What's the most under-used aggregate decision?
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Going up one size. A #3 floor reads more confidently than #2 in lobbies and large public spaces; most specifiers default to #2 because it's the standard.