Bold patterns, deep stories; this side of the building showcases some of the darkest, most dramatic slabs in the collection; deep blacks, shimmering flecks, and riverbed textures frozen in time. From volcanic gabbros to story-packed metaconglomerates, these rocks reveal powerful processes that shaped the Earth – and look amazing while doing it.
The slab numbers 7-15 are described below. CLICK each slab image to see a large, gloriously detailed version!
7. Gabbro; Cambrian Black, Canada (Quebec)
This sleek black rock is a gabbro, an igneous rock formed when magma cools slowly deep underground. That slow cooling gives crystals time to grow, which is why you can spot minerals like plagioclase feldspar, pyroxene, and olivine with the naked eye.
Granite vs. Gabbro: Both form from cooled magma, but granite is rich in silica (lighter in colour), while gabbro is loaded with iron and magnesium (making it darker and denser). That’s why gabbros like Cambrian Black are jet black or deep grey – perfect for dramatic design.
Learn more: details can be found at Geologyin.com.
8. Gabbro; Black Galaxy, India
Sparkles? Yes, please. Look closely at this gabbro and you’ll spot shimmering brown crystals of orthopyroxene, giving it a galaxy-like appearance that inspired the name.
Same rock type, different polish: This slab—and its cousin, Cambrian Black—are both gabbros, but may have different surface finishes (polished, honed, or sandblasted). Can you tell how this one was finished just by looking?
Look closely and you will see crystals of a highly reflective brown mineral called orthopyroxene in this gabbro.
Learn more:
– This type of Indian gabbro is described nicely by Shahin Dashtgard at his “WhatTheRock” website here (2022).
– The diversity of black “granites” is discussed in detail on the “Absolute Black Granite Guide” page at International Granites.
– Effects of different surface finishing such as polished, honed, sandblasted, etc. are illustrated with clever, interactive visuals at the PolyCor Natural Stone company’s Cambrian Black web page.
Think: Which finishing technique do you think we see with these two black Gabbro specimens.
9. Gneiss; “Asterix Granite, Brazil
This striking slab is often sold as “granite,” but geologists would call it a gneiss. The difference? Gneiss has been metamorphosed—heated and compressed until its minerals formed layers and bands.
Those bold streaks of black, grey, and red-brown make this a favourite in interior design, especially when paired with metals or wood. Look closely; don’t confuse shadows of a nearby tree with real rock patterns!
Think: Suppliers of stone for building call this a granite, but how can you tell that “gneiss” is a more appropriate term? (hint: see slab #4 above).
10. Gneiss; (label missing)
This slab tells a dramatic story. The bold swirls and folds you see are the result of intense pressure and heat that reworked the original rock—likely granite or sedimentary—into a gneiss.
Those alternating light and dark bands come from layers of quartz, feldspar, and biotite being stretched and recrystallized over time. The folding suggests that, deep underground, tectonic forces were at work, literally bending the rock without breaking it.
Fun fact: The slab was cut across these folds at just the right angle to highlight the dynamic flow of minerals—almost like a frozen ripple in the Earth’s crust.
11. Metaconglomerate; Verde Marinace, Brazil
This stunning slab is basically a fossilized riverbed. It started out as a mix of cobbles, pebbles, and sediments—igneous and metamorphic rock fragments carried by water and deposited in a muddy river channel many millions of years ago.
Over time, that riverbed was buried deep beneath the surface and transformed by heat and pressure into a metaconglomerate. The result? A rock that captures both motion and memory—rounded stones locked in place, telling a story of erosion, transport, burial, and rebirth.
Learn more: This type of Brazilian metaconglomerate is described nicely by Shahin Dashtgard (a geology professor at Simon Fraser U.) on his “WhatTheRock” website here (2023).
Think: What does the rounded nature and varied sizes of cobbles and pebbles tell you about the environment in which they were carried and finally deposited?
Think: Also, do the pebbles appear distorted or undeformed? This tells you whether the rock experienced strain while being slowly metamorphosed.
12. Metaconglomerate; Via Appia, Brazil
This rock has a backstory much like its neighbour, Verde Marinace (#11). It isa former riverbed packed with cobbles and sediment that was later transformed by heat and pressure into a metaconglomerate.
What sets this slab apart? Those striking reddish-brown streaks. They formed when iron-rich groundwater moved through the rock, leaving behind rusty stains that were later “baked in” during metamorphism. So yes, those bands really are ancient mineral stains, permanently locked into the stone.
Why Brazil? The country’s ancient, stable bedrock is a geologic goldmine. With billions of years of tectonic activity, Brazil’s crust is full of stunning and diverse rocks—many of which, like this one, now decorate buildings around the world.
Learn more: Why does Brazil have such a diverse range of amazing granite, gneiss and other building stone? See the brief introduction to Brazilian granite at Stone Forensics.
13. Gneiss; Golden Noir, Brazil
This eye-catching slab blends light and dark minerals in wavy bands – classic gneiss features. It’s made mostly of quartz and feldspar, with smaller amounts of biotite and oligoclase. That warm, reddish-brown sparkle? That’s garnet, a mineral that often forms during high-pressure metamorphism.
Unlike granite, which forms from cooling magma, gneiss started as a different rock—then got squeezed, stretched, and recrystallized deep underground. That pressure rearranged its minerals into bands, like you see here.
Think – try this: Can you figure out which direction this rock was compressed? The alignment of the bands gives clues to how tectonic forces shaped it, hundreds of millions of years ago.
Learn more: Geology students learn to interpret these kinds of observations in courses about petrology (EOSC 221 & others) and structural geology (EOAS 323 and EOSC 422). (Find more about courses for everyone or geologists in the introduction above.)
14. Magma Gold, Brazil
This dramatic slab is a migmatite—a rock born in two worlds. Part metamorphic, part igneous, migmatites form when extreme heat partially melts a rock like gneiss. The melted material (magma) swirls and mixes with the unmelted remnants, then solidifies into this one-of-a-kind swirling pattern of dark and light minerals.
The dark layers in Magma Gold are the original metamorphic rock; the golden veins are crystallized magma that forced its way in and froze mid-flow. It’s a geological mix-tape of materials, pressure, heat, and deep time.
15. Migmatite; Supreme, India
With its bold, ribbon-like layers, this rock really earns its name. This is a migmatite – a rock formed when intense heat nearly melts a metamorphic rock like gneiss. The lighter-coloured bands you see were once molten, made from minerals that melt at lower temperatures. That melt got trapped in place and cooled inside the remaining darker, unmelted material.
The result is a solid rock with a layered story. Some parts melted and crystallized like an igneous rock, while others stayed solid and transformed under pressure, like a metamorphic rock. It’s one rock, but it has lived two geological lives.Check out that symmetry! This slab was mirrored during cutting to enhance the natural folding pattern; a reminder that Earth’s processes often produce their own kind of artistry.