History - Andy Hay

Mont Saint-Hilaire is on of a group of plutons located on the St. Lawrence River lowlands. The Mont is about 25 miles east of Montreal, on the bank of the Richilieu River, a northward trending river that beings in the Lakes Region of New York and empties into the St. Lawrence River.

Mineral and fossil collectors, in their search for specimens, always seem to be just one step ahead of the ball-mill and the rock crusher. So it is here in the quarries that have been evacuated into the northeast face of this volcanic intrusion. Quarrying for cement rock and road metal began in 1959. Two adjacent quarries are found here: the Poudrette, and the Demix(formerly called the Desourette and the Unimix). A 1982 article on these quarries notes that the Demix had ceased operations, leaving only the Poudrette actively evacuating today. Collecting for minerals is strictly limited to field trips organized by the Club de Mineralogie de Montreal. As the quarrying operations continue at a face pace, new strata is constantly being exposed, bring new suites of minerals to light.

Geology - Sheila Bergmann

120 million years ago during the Cretaceous period, a plug-like body of magma pushed through layers of sedimentary rocks. Formed alkaline syenite rock rich in sodium, potassium and some rare earth elements. Other type of rocks formed were esserite and gabbro. In the metamorphric section, by melting some of the country rocks changed Hornfels and marble.

A. The magma stage was the original and produced the feldspars, nepheline, eudialyte and sodalite to crystal.

B. The next stage, a fluid gaseous stage, produced the dark minerals as aegirine, eudialyte, and others rich in Ti, Nd, Zr minerals

C. The third stage was the pegmatites. These were rich in F, Cd, S, and CO(2). The pegmatites, which are the residual portion of the magma and the last to have crystallized, can take the form of dikes, pipes and lenses. Minerals, Hackmanite, albite, more aegirine, high temperature rare earth and Ti minerals with formed. Sodalite and albite were in non- pegmatite rocks

D. The fourth stage was hydrothermal. This made Mont St. Hilaire what it is today. It made a whole series of mineral assocations and releases more elements by decomposition of earlier minerals. Albite and analcime replacement zones were formed. The rare earth minerals were replaced. Eudialyte altered to Catapeiite and elpidite.

E. The next stage was the weathering. This formed the hydrolated oxide minerals of manganese and iron. Chlorite came from the alternative aegirine and other pyroxenes and amphiboles.

The alkeline intrusive complex contains an abundance of agpaitic syenites. They form peralkaline minerals such as sodalite, aegirine, arvedsonite and rare sodium silicates with zirconium, titanium and rare earth elements.

Micromounts of Mount St. Hilaire - Kathy Dedina

Most of the minerals specimens from MSH are micro. 240 species have been found. These have a low silica content. The most common minerals occur in smaller amounts than world wide averages but carbonates and silicas have twice the world average—presence of rare earths. Most are found displaced in small openings in porous sections. Many have multiple crystal forms, adding to the difficulty of identification. They may have xomplex assembleges – one specimen may have 14 minerals. Thus one year may be a b onanza and the next year a bust. A trained eye is needed to spot a few specimens 0 lkook for bits of pink and or green amont the tons of rubble. Different suites are found in different sites.

Many look alike.

1. Green hole – vertical hole of pip in quarry = Elpidite crystal

2. Biotite hole depression found by mining yeilded interesting and new minerals.any

3. Igneous breccia – mottled green to grey color.

4. Hornfels- breccia

5. Hornfels – green rock- yellow crystal – narsarsukite

6. Marble zenoliths

7. Silicate vugs may host 60 rare species. Best species in center of rock.

8. Carbonate vugs

9. Pegmatites

10. Pink hole – seranolite pipe

Fluorescent Minerals of Mount Saint Hilaire - Kathy Dedina

Mont Saint Hilaire minerals are a variety of carbonate and silicate and the presence of numerous activators. Of 45 fluorescent materials 3 are silicates and 5 carbonates. Most of the fluorescent minerals are micros, as are the larger specimens. Good light needed under 15x needed but not all specimens of a mineral fluoresce.

Fluorescence reveals presence of trace elements and to identify any of these elements may be difficult in many cases.

Orange Fluorescence sphalerite mineral

Red Fluorescence some calcite

Lead is present in calcite of Mont Saint Hilaire. Cerium may be co-activator.

Uranium not listed as present but the the characteristic band had reveal Uranium present in green fluorescent analcim, apophyllite and monteregiante. Many other green Fluorescene minerals also due to Uranium except green of willimite due to Manganese..

Blue Fluorescence of Fluorite due to Eurapiun not listed as element present.

Green Fluorescence of Fluorite probably also a rare earth as is pink Fluorescence of laicp[jamote and pectolite

Orange Fluorescence of sodalite – sulfur.

Many of the rare minerals of Mont Saint Hilaire fluorescence and reflect mineral elements of sodium, Beryillium, titanium, and zirconium

Secretary - John Good

May Mineral Meeting

Topic – Minerals of Laurium, Greece

History – John Good

Geology – Sheila Bergmann

Minerals – Kathy Dedina

June Mineral Meeting

Minerals of Tsumb, Africa