February 13, 2018: Join MWF West Michigan Mineral Group in a study session to learn more about rocks and minerals. This is a free event led by a rock expert. More background details are listed below.
“In February we will continue our Aluminum mineral studies at Blandford Nature Center’s Learning Lab. The meeting at 7 to 8:30 pm on February 13, 2018 will feature minerals that contain Aluminum, but only those that begin with the letters ‘J’, ‘K’, or ‘L’. Let part of your collection get to meet some other rockhounds, and be appreciated by some members of the Blandford community, who should be joining us.”
Where: Blandford Nature Center: Learning Lab
Date: Tuesday February 13, 2018
Aluminum Minerals (G-I)
No better time than the start of a new year to look at some new mineral specimens. This month we looked at aluminum containing minerals that start with the the letters G, H, or I since we can only look at about 25 minerals in the 90 minutes that we meet (and it is a good night if we have over 10% of the minerals from the complete list).
Our habit is to pass our topic 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. It is one thing to look at the pretty pictures in the field books, but you get a much deeper appreciation when you can hold a specimen in your hand, and look at it thru a lens (feel the density, shine a bright light on it, look at it under black light, etc.). And then examine another specimen of the same mineral (and yet another).
We started this month with the oxides Gahnite and Galaxite, the inosilicate Gedrite, the sorosilicate Gehlenite and the oxide Gibbsite, which is one of only three trihydroxides of Aluminum.
We spent some time looking at a mystery specimen that had been tentatively identified as containing Glauconite (green) or Glaucophane (blue/green). Than it was the tectoslilicates Gmelinite-NA, Gonnardite, and Goosecreekite, and the sulphate Grandviewite, a turquoise-colored mineral known only from the Grandview Mine that was not formally named and described until 2007. The Grandview Mine is on Horseshoe Mesa in the Grand Canyon. The specimen came from old survey samples collected before the National Park was formed.
We continued passing specimens with the nesosilicate Grossular, the phylosilicate Gyrolite, two ancient tectosilicates Harmotome and Hauyne (named before -ite was the accepted ending for minerals). Then it was the phylosilicate Hendricksite, the tectosilicate Heulandite-Ca, the oxide Hibonite, and the inosilicates Holmquistite, Hornblende, and Howieite. We found a couple of the presented hornblende specimens were actually elbaite.
We ended with the cyclosilicate Iolite. A theory exists that the sunstone had polarizing attributes and was used as a navigation instrument by seafarers in the Viking Age. An Iolite sunstone found in 2013 off Alderney, in the wreck of a 16th-century warship, may lend evidence of the existence of sunstones as navigational devices.
In February we will continue our Aluminum mineral studies at Blandford Nature Center’s Learning Lab. The meeting at 7 to 8:30 pm on February 13, 2018 will feature minerals that contain Aluminum, but only those that begin with the letters ‘J’, ‘K’, or ‘L’. Let part of your collection get to meet some other rockhounds, and be appreciated by some members of the Blandford community, who should be joining us.