Elise Skalwold's Photo Gallery
T54-4Y4Calcite (Var: Iceland Spar) CaCO3
Dimensions: 65 mm x 45 mm x 35 mm
The original Iceland Spar cleavage rhomb with which Norwegian-American Leif K. Karlsen tested his theory of Viking navigation. Origin: Iceland, probably Helgustadir locality; a gift on one of his visits to Iceland during his research for his 2003 book "Secrets of the Viking Navigators." Leif carved the wooden box to keep it safe in.
Skalwold, E.A. and W.A. Bassett. (2015) Double Trouble: Navigating Birefringence. Chantilly, VA: Mineralogical Society of America. 20 pages. ISBN 978-0-939950-02-7 Booklet download on the MSA website: http://www.minsocam.org/msa/openaccess_publications/#Skalwold_01
Abstract: "Optical mineralogy has many fascinating though often complex concepts which underlie common effects observed in minerals and lapidary specimens fashioned from them. Doubling of images such as seen through a calcite rhomb is perhaps one of the most readily observed of these properties and could well have been one put to use centuries ago in a very practical way. The intriguing theory of the Viking’s use of a coveted stone to find their way in arctic waters has its roots in the ancient Viking Sagas, optical mineralogy, and in practical application by modern navigators. The proposed minerals thought to be the Viking “sunstone” are excellent models for understanding the optical phenomena of birefringence and pleochroism; the very properties which make them useful for navigation are also those which make them valuable to mineral and gem enthusiasts today (see Skalwold 2008). There are several candidates for the stone. Among them are “Iceland Spar” calcite of which a coveted optical-quality variety was found abundantly in eastern Iceland, and the blue variety of the mineral cordierite, found in Norway and popularly known as “Viking’s Compass” and as the gem “iolite.” While the latter’s extraordinary pleochroism is explored in the authors’ article “Blue Minerals: Exploring Cause & Effect” (Skalwold and Bassett 2016), the more likely candidate, Iceland spar, is the classic model for demonstrating the phenomenon of birefringence and doubling in optically anisotropic minerals. However, whether one’s adventures with minerals are land-bound or at sea, before venturing far there is some trouble with doubling to untangle first."
6CU-VH5Quartz SiO2
Dimensions: 60 mm x 65 mm x 40 mm
Quartz, Hot Springs, Arkansas; ex. Dr. R.W.M. Woodside collection; Seattle Mineral Market May 2015.
Skalwold, E.A. and W.A. Bassett. (2015) Quartz: a Bull’s Eye on Optical Activity. Chantilly, VA: Mineralogical Society of America. 16 pages. ISBN 978-0-939950-00-3 Booklet download on the MSA website: http://www.minsocam.org/msa/openaccess_publications/#Skalwold_02
Abstract: "It might be overstating a bit to say that if one could understand all there is to know about quartz, then everything else in the universe would make sense. Without doubt, this mineral has profoundly impacted many sciences and technologies which we rely upon today. At the very least, quartz provides one with a host of mental gymnastics and a seemingly endless variety of puzzles to ponder. Not least among its fascinating properties is that of optical activity, its manifestation of which results in the special optical figure affectionately known as the “bull’s eye.” In the authors’ article on causation of blue color in minerals, mention is made of the quartz monochromator, an obscure instrument which makes use of optical activity in a very elegant way (Skalwold and Bassett 2016). In hopes of giving readers insights and appreciation for this ingenious device and for quartz itself, the following is an exploration into the nature of the chromatic phenomenon which plays out within this proverbial black box."
LHJ-TXAAnorthite (Var: Labradorite) (Ca,Na)[Al(Al,Si)Si2O8]
Dimensions: 63 mm x 35 mm x 10 mm
“Shades of Blue Minerals,” the January/February issue of Rocks & Minerals magazine, has recently been posted online and the glossy hardcopy is soon to follow via snailmail, just in time for the ramp-up to the 2016 Tucson Gem & Mineral Show of the same theme! I’m thrilled to have been invited to write about the mechanisms of color for this special issue, and hope the somewhat different approach to this topic will be helpful to those interested in minerals and gems. Nearly a year in genesis, the article is aimed at a wide-range of interest levels and backgrounds. It’s also the first in a series of popular science articles focused on optical mineralogy and crystallography; the next two already-completed installments will come out very soon.
On-going collaboration with Cornell’s Professor Emeritus William A. Bassett is truly priceless to me for this and other projects in the wings, as well as for those over the past eight years of work and research together. Bill shares my enthusiasm for exploring the fascinating aspects of this classical science, and as my co-author he sets the highest bar for accuracy. I’m so honored that these efforts have resulted in this article being included in such a fine publication as Rocks & Minerals, a cross-discipline geological periodical chock-full of diverse topics. R&M has one of the toughest editorial review boards in the mineral world, as well as a community of some of the most engaging writers of the genre. As to why some minerals (and feathers) are brilliant blue when light falls upon them yet in transmitted light are revealed to be colorless, see “Blue Minerals: Exploring Cause & Effect.”
Abstract: http://www.rocksandminerals.org/Back%20Issues/2016/January-February%202016/blue-minerals-exploring_abstract.html
Skalwold, E.A. and W.A. Bassett. (2016) Blue minerals: exploring cause & effect. Rocks & Minerals, Vol.91, No.1, pages 61-75.
QJJ-YUTPezzottaite Cs(Be2Li)Al2(Si6O18)
Dimensions: 8.32 mm x 7.60 mm x 5.80 mm
Weight: 2.33 carats
Note: This doubly terminated crystal shows strong eye-visible pleochroism perpendicular to the optic axis/c-axis (orangy/purplish red in polarized light).
Reference: Skalwold, E.A. and Koivula, J.I. (2015): Pezzottaite Debuts as the Newest Trapiche Gem Mineral. Gems & Gemology, 51 (3), 326-328.
http://www.gia.edu/gems-gemology/fall-2015-microworld-pezzottaite-debuts-trapiche-gem-mineral
95L-VM0Meliphanite (Ca,Na)2(Be,Al)[Si2O6(OH,F)]
Dimensions: 90 mm x 65 mm x 35 mm
This specimen is in Cornell's Timothy N. Heasley Mineralogy Museum collection. The original label states only: "Meliphane, Barkevig, Norway" - perhaps from Langesundfjorden area (Barkevik). I have a soft spot for Norwegian minerals and uploaded this one because Alfredo liked it: "Very nice meliphanite! Looks like it even has some rounded crystal terminations."
