Dallasite: Vancouver Island’s Volcanic Mosaic Stone

By Adam Kelliher
Published Sep 30, 2026 · Updated Oct 18, 2026

Dallasite is one of Vancouver Island’s most recognizable lapidary rocks.

At its best, it looks like a natural mosaic: green, black, white, grey, cream, and sometimes yellowish fragments locked together in sharp broken patterns. Some pieces look like shattered glass. Others look like green islands floating in pale quartz or carbonate. Cut well, it can make bold cabochons, slabs, pendants, and display pieces.

But Dallasite is not a mineral.

It is a rock name, mostly used by collectors and lapidary people, for a distinctive altered volcanic breccia found on Vancouver Island.^[1]^[2] More simply:

Dallasite is broken underwater volcanic rock that was later healed by minerals.

That is why it looks fractured, sealed, and patterned all at once.

Why Is It Called Dallasite?

The usual story is that dallasite is named after Dallas Road in Victoria. Gem databases repeat it,^[2] and so does Wikipedia, but I haven't found a primary record (a dated club bulletin, newspaper item or survey report) that actually documents the naming. So treat the Dallas Road origin as unconfirmed. It's a good story, not a proven one.

There's also a geological wrinkle. The thick pillow-breccia rock that dallasite comes from is mapped mainly in the Karmutsen basalts of central and northern Vancouver Island (more on that below).^[1]^[4]^[5] Victoria's own surface is glacially scoured bedrock, often under a thin skin of Vashon till.^[6] At Harling Point on the Dallas Road shore, a VIU teacher field guide describes deformed ribbon chert and siltstone, plus glacial erratics carried in from elsewhere.^[7] My read, and it is only inference: if dallasite cobbles turn up on Dallas Road beaches, they most likely travelled there with the ice or the till, rather than weathering out of the cliffs.

Either way, the name is local and lapidary-based, not a formal mineral species. Not every dallasite specimen comes from Dallas Road, and not every green-and-white rock near Dallas Road is dallasite.

A clean definition: dallasite is a Vancouver Island lapidary name for a distinctive altered volcanic breccia, reportedly named for Dallas Road in Victoria.

Dallasite Begins With Basalt

To understand Dallasite, start with basalt.

Basalt is a dark volcanic rock. It commonly forms from lava that erupts at or near the surface. On Vancouver Island, large areas of bedrock are made of old basaltic volcanic rocks. These rocks are part of the island’s deeper story: ancient oceanic crust, volcanic arcs, accreted terranes, and seafloor environments later added to the western edge of North America.

Some of that lava erupted underwater.

When basaltic lava enters water, the outside cools quickly. The surface can freeze into a glassy skin while the inside remains hot and moving. This often creates rounded, bulbous shapes called pillow basalt.

Pillow basalt is one of the clearest signs that lava erupted beneath water.

But pillow lava does not always stay neat. Its chilled outer rims can crack, spall, shatter, and break apart. Broken volcanic glass and pillow-rim fragments can accumulate as angular volcanic rubble. This kind of broken underwater volcanic material may be called hyaloclastite, pillow breccia, or volcanic breccia, depending on the details. In the Karmutsen basalts of northern Vancouver Island, BC Geological Survey mappers describe elongate to curvilinear shards from the spalled rims of pillows, partly altered to chlorite, epidote, quartz and carbonate, “for which the local term ‘dallasite’ has been coined.”^[1]

That broken volcanic material is the starting point for Dallasite.

The Karmutsen Formation: Where the Breccia Comes From

The host rock has a formal name: the Karmutsen Formation, flood basalts of the Wrangellia terrane that cover about 20,000 km² of Vancouver Island and were erupted around 225 to 230 million years ago, in the Late Triassic.^[4]

What makes the Karmutsen perfect for dallasite is how it's stacked. From the bottom up, Greene and co-authors describe a sediment-sill complex, more than 2.5 km of pillowed submarine lava, more than 1.5 km of pillow breccia and hyaloclastite, then more than 2.5 km of massive lava flows erupted on land.^[4] That middle unit is the moment the volcanoes broke the sea surface: lava hitting water, pillow rims shattering into shards, and the rubble piling up. It's the dallasite layer, as far as I'm concerned, although no source I've read tests a cut dallasite slab against a specific map unit.

As for the colours: BC Geological Survey mapping on northern Vancouver Island describes the finely broken interpillow material and hyaloclastite as "locally cemented and veined by white zeolites," with quartz, epidote, chlorite and carbonate as other common vein minerals.^[5] White, cream, green and grey. That's the dallasite palette.

The Mosaic Came Later

Dallasite: Volcanic mosaic stone

Broken basalt alone does not make good Dallasite.

The pattern forms when the broken volcanic rock is altered and cemented. Mineral-rich fluids move through the fractured material. Those fluids change the original basalt and volcanic glass. They also fill cracks and open spaces with new minerals.

That is where the colour and contrast come from.

The green is commonly tied to minerals such as chlorite and epidote. Pale areas may include quartz or carbonate. Dark fragments may be basaltic material or more heavily altered volcanic pieces. The exact mix varies, which is why Dallasite can look so different from one piece to the next.

The formation sequence is simple:

Basaltic lava erupted underwater.
The lava formed chilled pillow margins.
Those margins broke into angular fragments.
Mineral-rich fluids altered the broken rock.
Quartz, epidote, chlorite, carbonate, and related minerals filled and cemented the spaces.
Erosion, waves, rivers, and glaciers later exposed and moved pieces into places where people could find them.

Dallasite looks broken because it was broken.

It looks healed because it was healed.

Why Dallasite Is Often Called Jasper

Collectors often call it Dallasite jasper or Vancouver Island jasper.

That name is understandable, but it is not perfect.

In lapidary use, “jasper” often means a hard, opaque stone that takes a polish. By that standard, good Dallasite can behave like jasper. It can be cut, shaped, polished, and worn.

Geologically, jasper usually means opaque microcrystalline quartz. Dallasite is more complicated. It is not just silica. It is a volcanic breccia with altered basalt fragments, quartz, carbonate, epidote, chlorite, and other minerals.

So the most honest phrasing is:

Dallasite may be sold as jasper, but it is better explained as an altered volcanic breccia.

Jasper explains the trade habit. Breccia explains the stone.

Why Vancouver Island Has Dallasite

Vancouver Island has Dallasite because it has the right volcanic history.

Much of the island belongs to Wrangellia, a major geological terrane that includes thick packages of basaltic volcanic rock. The island also contains varied volcanic and volcaniclastic rocks, including flows, breccias, tuffs, and fragmental volcanic units. Some formed in underwater settings. Some were later altered, fractured, buried, uplifted, eroded, and reworked.

Dallasite needs several ingredients:

basaltic lava
underwater cooling
broken pillow-lava fragments
mineral-rich fluids
open spaces and fractures
later exposure by erosion

Vancouver Island has all of those.

That is why Dallasite is more than a pretty local stone. It is a small, cuttable piece of the island’s volcanic past.

Where to Find Dallasite

Dallasite is a Vancouver Island stone. The thickest pillow breccia and hyaloclastite described by the BC Geological Survey is on central and northern Vancouver Island,^[1]^[4]^[5] but cobbles get moved around by ice, rivers and waves, so collectors also look in beach cobbles, creek beds, gravel bars and areas draining volcanic terrain.

Good places to think about are not “magic secret spots.” They are geological settings:

beaches with mixed volcanic cobbles
creeks cutting through basaltic terrain
gravel bars below volcanic bedrock
storm-washed cobble beaches
areas where pillow basalt or volcanic breccia is naturally breaking down
southern Vancouver Island coastal sites
east Vancouver Island beaches and river systems

Access changes. Some places are private, protected, culturally sensitive, unstable, or restricted. Beaches also change after storms, tides, and seasonal erosion.

The practical rule is simple:

Look where volcanic rock is naturally being broken, moved, and concentrated.

That usually means beaches, creeks, rivers, and gravel bars — not random dirt banks.

How to Recognize Dallasite

How to Recognize Dallasite, black green, white mosaic rock

Dallasite is easiest to spot when wet or freshly cut.

A dry cobble may look dull. Water often reveals the pattern.

Do not assume every green-and-white stone is Dallasite. Vancouver Island has many altered volcanic rocks, epidote-rich rocks, quartz-veined rocks, and glacially transported cobbles.

Look for:

angular broken fragments
green, black, white, grey, or cream contrast
quartz or carbonate-filled cracks
hard, dense texture
volcanic-looking dark pieces
mosaic-like structure
pattern running through the stone, not just surface staining

A field guess is useful. A saw cut is better.

Why Some Dallasite Cuts Well and Some Does Not

Dallasite can be excellent lapidary material, but it is not always cooperative.

The problem is mixed hardness.

Quartz-rich areas may polish well. Softer carbonate or chlorite-rich areas may undercut. Fractures can open. Weathered pieces can crumble. Some material looks great wet but falls apart on the saw. Other pieces look plain outside and reveal strong pattern inside.

The best cutting rough is usually:

solid
heavy for its size
not deeply weathered
not crumbly on the edges
not full of open fractures
patterned through the stone
clean enough to take a polish

With Dallasite, selection matters. The same geological complexity that creates the pattern can also make the stone difficult to cut.

That is the trade-off.

Dallasite vs Flowerstone

Dallasite is often mentioned alongside other Vancouver Island lapidary rocks, especially flowerstone.

They are not the same thing.

Dallasite is a breccia story. It is broken volcanic material healed by later minerals.

Flowerstone is a texture story. It is a glomeroporphyritic rock: clusters of feldspar crystals grow in a fine-grained volcanic groundmass and form flower-, snowflake- or “mouse-track”-like patterns. The name is used for such rocks from Texada and Vancouver islands.^[3]

Both are tied to Vancouver Island’s volcanic history. Both can be attractive. Both can confuse beginners. But they are not interchangeable.

A useful field distinction, based on how each rock formed, is:^[1]^[3]

Dallasite looks shattered and healed. Flowerstone looks spotted, radiating, or flower-like.

That is not a perfect scientific test, but it is a good starting point. Don’t confuse flowerstone with “chrysanthemum stone,” an orbicular gabbro from near Victoria, which is a different rock again.^[3]

Is Dallasite Valuable?

Dallasite is not precious in the diamond-ruby-emerald sense.

Its value comes from locality, pattern, hardness, polish, and lapidary quality. Common, fractured, muddy material is not worth much. Strongly patterned, solid, well-cut material is more desirable.

Good Dallasite has:

strong contrast
tight structure
clean polish
attractive pattern
recognizable Vancouver Island identity

It is a local collector and lapidary stone, not a high-value gemstone. That is not a criticism. Some rocks are interesting because of place, texture, and story, not because they are expensive.

Why Dallasite Is Worth Understanding

Dallasite teaches several geology lessons at once.

It shows that lava can erupt underwater. It shows that volcanic rocks can break apart while forming. It shows that fluids can alter and cement broken rock. It shows that colour comes from mineral chemistry. It also shows why a lapidary stone can be beautiful and difficult for the same reason.

Dallasite is damage plus repair.

It began as volcanic rock. It broke. It altered. It healed. Then Vancouver Island’s erosion, rivers, waves, and collectors brought it back into view.

That is the real appeal.

Not just “green rock.”

Not just “jasper.”

A local volcanic mosaic.

Dallasite in One Sentence

Dallasite is a Vancouver Island lapidary stone formed from broken underwater basaltic volcanic rock, later altered and cemented by minerals such as quartz, epidote, chlorite, and carbonate.

It is not one mineral.

It is a geological mosaic.

References

Nixon, G.T., Larocque, J., Pals, A., Styan, J., Greene, A.R. and Scoates, J.S. (2008). High-Mg lavas in the Karmutsen flood basalts, northern Vancouver Island (NTS 092L): stratigraphic setting and metallogenic significance. In Geological Fieldwork 2007, BC Ministry of Energy, Mines and Petroleum Resources, Paper 2008-1, pp. 175–190. PDF
Gemdat.org. Dallasite gemstone information. gemdat.org/gem-27169.html
Central Michigan University, GemRocks: Porphyry (entries for “Flowerstone” and “Chrysanthemum stone”). stoneplus.cst.cmich.edu/porphyry.htm
Greene, A.R., Scoates, J.S., Weis, D., Nixon, G.T. and Kieffer, B. (2009). Melting history and magmatic evolution of basalts and picrites from the accreted Wrangellia oceanic plateau, Vancouver Island, Canada. Journal of Petrology 50. doi:10.1093/petrology/egp008 (free copy: BCGS EXT063)
Nixon, G.T., Hammack, J.L., Koyanagi, V.M., Payie, G.J., Panteleyev, A., Massey, N.W.D., Hamilton, J.V. and Haggart, J.W. (1994). Preliminary geology of the Quatsino–Port McNeill map areas, northern Vancouver Island (92L/12, 11). In Geological Fieldwork 1993, BC Geological Survey Paper 1994-1, p. 67. PDF
Monahan, P.A. and Levson, V.M. (2000). Quaternary Geological Map of Greater Victoria. BC Geological Survey Geoscience Map 2000-2. PDF
MineralsEd and Vancouver Island University Earth Science Department (2016). Victoria Area Geotour (teacher field guide), Stop 3, Harling Point. PDF