Collecting Crystal in Ontario Pegmatites

Hunting Hidden Treasures: How Crystal Collectors Find Pockets in Pegmatites and Vein-Dykes

​

Defined, a pegmatite is a coarse grained igneous intrusive. By any measure, the Dark Star claims are a rockhound’s playground. Most visitors come for the vein dykes—broad ribbons of calcite that slice through the forest floor—but pegmatites run through these hills as well, and both types of formation can conceal spectacular crystal pockets. Because some excavations take days before yielding even a hint of reward, experienced collectors learn to quickly “read the rock” and identify places where pockets are most likely to occur.

​

 

 

 

 

 

 

 

 

 

 

 

Pegmatites in an area tend to share a similar mineralogy and around the dark star claim the local formations tend to distinguish themselves by bearing molybdenum. Just east of there the syenitic pegmatites of the Wilberforce area are the oldest in Ontario, while    those at Hybla have a predominance of rare earth minerals and are the youngest        (measured in billions of years). The apatite mines of eastern Ontario tend to be have been sunk into pyroxenite pegmatites. The apatite used to be crushed for phosphate fertilizer. The Leduc Mine in Wakefield Quebec is just across the Ottawa River and sunk into a local pegmatite. Last time I visited there were lovely green tourmaline's with clear cores.

​

As a general observation it is often a rusty gneiss into which Ontario’s pegmatites have protruded. Surface pockets are rare, and when they do appear, they are usually weathered and crumbled beyond collecting. The real treasures lie hidden underground. As we say at Dark Star Crystal Mines, “You gotta get below the frost line”.

​

Pegmatites: Following the Core

​

Pegmatites are perhaps the most intuitive structures to read. In these coarse-grained granitic bodies, crystal size increases toward the center, creating a natural guide for collectors. The core—usually the thickest part of the pegmatite, roughly halfway between its margins—is the most favorable location for pockets.

​

​

​

​

​

​

​

​

​

​

​

​

​

​

 

 

 

 

 

Mineral changes also provide clues. Large feldspar grains, growing steadily larger toward the middle, signal that you’re moving deeper into the system – getting closer to the center where the gems are, elbaite tourmaline, gem zircons and stunning red and blue beryls. But the pattern is not always perfect. Sometimes a band of fine-grained apalite interrupts the transition. This layer, formed when temperature or pressure suddenly dropped. It marks a disturbance within the pegmatite—a sudden change in temperature or pressure. Much as apalite marks physical events, apatite, the gem of the Ottawa Valley records chemical changes that have taken place.

​

Imagine a 100-foot-long pegmatite, exposed from end to end and averaging five feet across. Along its length, several swellings bulge to nearly ten feet. Many of these contain only massive feldspar—tough, solid, and devoid of accessory minerals. But one swelling breaks the pattern: quartz and mica appear alongside a loosely packed matrix that crumbles under your pick. Glassy quartz and pink mica come out effortlessly. This is the kind of mineralization that signals that you are at the edge of a pocket-rich zone, elsewhere the quartz is cloudy.

​

​

​

​

​

​

​

​

​

​

​

​

 

 

 

Pegmatite pockets can be surprisingly deep, and on the surface they are often hidden beneath saplings and brush that take root in the loose, decomposed material of the mid-line.

​

Vein Dykes: Treasure Along the Edges

​

Vein dykes behave differently. Their best pockets typically occur along the margins—especially where two rock or mineral types meet. Calcite-filled dykes can contain random cavities, but these often taper into water-worn tunnels where crystals become trapped in the flow beds. These features may continue for surprising distances, although the pockets themselves can be scattered, irregular, and unpredictable.

​

Though calcite is not commonly regarded as a pegmatite mineral, the MacDonald feldspar mine has huge amounts of calcite that in places yields ellsworthite, titanite and smoky quartz. Running  through the 1920s in a zoned granitic pegmatite they shipped 5000/tons of feldspar per year from  nearby Hybla station. I recall the enormous cavern that had been excavated at the bottom of the trench and the feldspar crystal – big as a refrigerator up near the roof. Though the entrance has now been shoveled in it is considered to be one of the more unique Canadian pegmatites.

​

​

​

​

​

​

​

​

​

​

​

​

 

​

 

 

Historic Workings: Windows Into

the Past

​

Old mines and quarries often expose pocket-bearing areas that would otherwise require hours of excavation. Along Noggie’s Creek, for example, a 1950s adit plunges about 100 meters into a hillside, intersecting the core of a pegmatite. In its dim tunnel walls, flashes of peacock-blue peristerite glint from the rock. Yet it’s worth remembering that historic miners frequently avoided pegmatite cores altogether—they were after pure feldspar or quartz, not the accessory minerals gem collectors so greatly prize.

​

​

​

​

​

​

​

​

​

​

​

​

​

Breaking Into a Pocket

​

The outer edges of a pocket reveal themselves gradually. Feldspar crystals grow larger and begin to point inward. Tree roots often betray the location of hidden cavities, slipping like a squid’s tentacle into the loose, rotten pocket material of a pegmatite pocket long before a human notices it.

​

At the pocket’s threshold, feldspar may be draped in yellow-green mica or pierced by thin tourmaline needles. Quartz usually shifts from milky to transparent, sometimes taking on colours ranging from clear to smoky, amethystine, or even rose. Black tourmaline (schorl) begins as thin triangular crystals at the pegmatite’s edge and they thicken toward the center, sometimes transitioning into multicolored elbaite where lithium is present.

​

​

​

​

​

​

​

​

​

​

​

 

 

 

Beryl often appears first as pale, fractured lumps but becomes graceful and gem-quality closer to the pocket’s heart. Mica books grow larger too—silver on the outside, shading into yellow or green within, sometimes rimmed in purple where lithium enriches the material into lepidolite.

​

Local pegmatites may also host a wide range of accessory minerals, including apatite, fluorite, spodumene, monazite, phenakite, and more. At the famous Beryl Pit near Quadeville, Ontario, phenakite is often found alongside beryl, though the true core of that pegmatite remains undiscovered and every few years they have another go with the dynamite.

​

Pegmatite Swarms and the Rockhound’s                                  Mindset

​

​

​

​

​

​

​

​

​

​

​

 

Pegmatites rarely occur alone. More often they form in swarms, sharing similar mineralogy, structural orientation, and dip angle. In fields where dozens or even hundreds are exposed, collectors quickly learn a key lesson: 90% of pegmatites may be barren, but the remaining 10% can be extraordinary.

​

The same is true of vein dykes. A plain, simple calcite dyke may sit directly beside one that erupts with spectacular crystals. Persistence—and a willingness to dig, read, and explore—is the rockhound’s greatest ally.

​