At Our Meeting: Monday, November 13, 2006
Program: Ken Casey presented "The Colors of Fluorite".
Ken shared with us what gives fluorite its range of colors, and the
science behind "fluorescence". He demonstrated with a slide show and
numerous specimens from his collection.
Ken gave away three specimens (one each) to the the first three members,
visitors, or guests who answered a fluorite question. You guys did your homework!
Study Links
Ken's
PowerPoint Slideshow (17MB)
Fluorite: A
Global Quest for the Perfect Crystal
Fluorites
of Antarctica: An Unspoiled Treasure
Fluorite (mindat.org)
Program Review:
At our November 13, 2006 meeting we were immersed in the world of colorful
fluorites. As I am both the author and this program review, I'll humbly recount our
meeting's program. So, I'll get to speak in the first person.
Fluorites are a specialty of mine. I've been intrigued by them for
many years. After noting their fluorescent properties, I became doubly-delighted.
With a couple of years intense study into fluorite's geology, chemistry,
crystallography, and color, I thought I was ready to offer a full program to my fellow DMS
Members. So, Tom Pankratz, our VP of Programs put me on the bill.
I choose to present with a common thread to some of our past presenters:
the color of minerals. Focusing upon U. S. locales, I heavily researched and put
together a 60 slide Microsoft PowerPoint presentation with a myriad of colorful samples.
Some were from my personal collection; others were from collectors, sellers, and
photographers around the globe.
To support my topic of color, I brought in several specimens to
demonstrate crystal types and in-person color and type comparisons. I was thrilled
that so many members came up to talk with me before and after the presentation, and to
look at my personal collection. It was nice to be among friends.
During the presentation, several members asked questions about locales,
chemistry, and the frequency of color ranges. To answer Tracy's question about a
locale, the Oatman District is in Mohave County, Arizona.
To generate enthusiasm about fluorite and sharing, I awarded three members
with specimens from my personal collection. Each only had to answer a pertinent
fluorite question from our program.
New member Jim Stauffer answered the question of the basic chemical
formula of Fluorite. Of course, he knew it was CaF2. He received a
nice, gemmy green, botryoidal fluorite from Hunan Province, China.
Fran Poniecki correctly identified two of many lapidary projects
represented on a couple of slides. He won a handful of fluorite lapidary rough from
three locales.
Junior Member, Daryl, knew upon which continent scientists have found the
rarest occurrence of fluorite: Antarctica. (See our MOTM article "Fluorites of Antarctica:
An Unspoiled Treasure".) Though I couldn't offer him fluorite from that
continent, I did award his knowledge with several colorful and natural octahedral
crystals.
I covered the chemistry and physics of atomic-level coloring, and optical
properties in a modest depth. Science still has more to discover about individual
colors, like pinks and reds, from specific locales, like Durango, Mexico, for example.
Most members seem to have enjoyed the colorful, "wow" photos of
premier specimens from many famous U. S. and world locales. We visited eleven sites
in our country, and touched upon global sites. My research showed that 42 states
have proven mines or collecting locales. Eric Meier mentioned to us that he has
knowledge of specimens from Washington State. (I'll have to update my maps now.)
I enjoyed members sharing collecting stories and info on our favored
mineral this month. That's how we like doing it in the rockhounding community.
I added that the purple fluorites occur in our club's nearby Pennsylvania
fieldtrip locales. And, that Bob Asreen has made active quarries accessible to
members several times a year.
Collectors might find that some PA cubes could be found, depending upon
what nature has left in the ground, and the quarrymen have blasted out for us at certain
dates. These gemmy purples crystals form often with calcite and pink dolomite.
More rarely, they can occur with sphalerite or pyrite.
I was fortunate enough to attend one of our fieldtrips, between our
program and this writing, to the Binkley-Ober quarry in
East Petersburg, PA. On that day, Karissa found some wonderful assemblages of
dolomite and millerite. She also came across nice micro yellow barite crystals in
pink dolomite, with purple fluorite! (I'll post some pictures.)
Before and after the meeting, I offered a modest quantity of green and
purple gem rough for sale at my cost to promote the wonderful colors of fluorite.
Bob Todd took home a few carats. I'm curious to see what Bob will make from
these. Please do show us, when you're ready, Bob.
It was a joy to share with our members about the colors of fluorite.
Thanks for taking part. See you next meeting.
--Ken
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