Event: MWF West Michigan Mineral Study Group– Aluminum Minerals (B-C)


November 14, 2017: Join MWF West Michigan Mineral Group in a study session to learn more about Aluminum Minerals (B-C). This is a free event led by a rock expert. More background details are listed below.

Where: Blandford Nature Center: Learning Lab

Date: Tuesday November 14, 2017

Time: 7pm-8:30pm

Cost: Free


Aluminum Minerals (B-C)

Aluminum is the third most abundant element in the Earth’s crust and there are too many minerals that contain it for us to review them in one meeting in the Blandford Nature Center’s Learning Lab. This month we looked at aluminum containing minerals that start with the the letters B or C.

Our habit is to pass our specimens around the table in alphabetic order, one mineral at a time, and share some facts about the mineral. Sometimes it may be one specimen, or sometimes everyone there may have brought at least one specimen.We started this month with the oxide Bahianite, the tectosilicate Barrerite, the inisilicate Bavenite, the phylosilicate Beidellite and the cyclosilicate Beryl.

Beryl brought out the varieties Aquamarine, Emerald, Heliodor, Goshenite, and Morganite. New England’s pegmatites have produced some of the largest beryls found, including one massive crystal from the Bumpus Quarry in Albany, Maine with dimensions 18.0 by 3.9 ft with a mass of around 18 metric tons; it is New Hampshire’s state mineral.

We looked at the tectosilicate Bikitaite. Then came Biotite, which is now a Group name that MinDat says is used as a generic field term for any incompletely analysed dark mica. This also brought out a specimen of Phlogopite. Then we backtracked to look at the principle ore of Aluminum, the rock Bauxite.

Then we got back on track with the halides Brewsterite-Ba and Brewsterite-Sr, the phosphate Cacoxenite, the tectosilicate Cancrinite, the inosolicate Carlosturanite, the phosphate Ceruleite, and the tectosilicate Chabazite-Ca. Most of our specimens were not analyzed so we did not know the suffix (Ca, K, Mg, Na, or Sr). We had a side discussion about the dominant member of mineral species that leads to a suffix.

Back to our laps with the sulfide Chalcoalumite, the phylosilicate Chamosite, the phosphate Childrenite, the halide Chiolite, and the oxide Chrysoberyl, var. Alexandrite. This sparked a discussion about pleochroism, which is an optical phenomenon in which a substance has different colors when observed at different angles, especially with polarized light.

Then we realized we were running out of time, so we had a sprint lap with the cyclosilicate Chrysocolla, the tectosilicate Cleavelandite, the phylosilicate Clinochlore, the tectosilicates Clinoptilolite-Ca and Clinoptilolite-Na, the Sorosilicate Clinozoisite, the phylosilicate Cookeite, and the cyclosilicate Cordierite. This is a dimorph of Indialite that also exhibits pleochroism and is structurally related to Beryl (also exhibits pleochroism).

The oxide Corundum also brought out its sparkly varieties Sapphire and Ruby. And then it was down the home stretch with the tectosilicate Cowlesite, the halides Creedite and Cryolite, the sulfate Cyanotrichite, and the sorosilicate Cyprine.

A flat of specimens from the 79 Mine in Arizona was donated to the study group and all who attended went home with one. We had a discussion on how to use the MinDat location search to help identify minerals.