Annotated list of references on Iceland spar and polarized light

-1921 Halle, D., describes his methods….zur Ersparnis des immer kostbarer werdenden
Rohmaterials…in the production <strong>of</strong> various types <strong>of</strong> Nicol prisms.
- 1922 The Minister for Industries, Iceland, states in Parliament that there is great
demand from many quarters for optical-quality spar.
-1922 Tutton, U.K. Large crystals are now becoming rare and exceedingly valuable
…Such large prisms can now no longer be made, the original magnificent deposit <strong>of</strong>
enormous clear rhombs <strong>of</strong> Iceland spar at Eskifjördhr having become exhausted …There
is, happily, plenty <strong>of</strong> smaller calc-spar constantly being discovered, so that Nicol prisms
for all ordinary crystallographic apparatus and the polarising microscope are more or less
readily procured…
- 1923 Glazebrook, U.K., describing construction <strong>of</strong> Nicol prisms: …have sought the
ideal mean between a prism <strong>of</strong> greatest utility and one involving small waste <strong>of</strong> material,
an almost equally important consideration owing to the small supply <strong>of</strong> large flawless
crystals <strong>of</strong> Iceland spar.
-1924 Stöber, D. … Da die isländische Kalkspatgruben, die einzigen, welche für den zu
optischen Zwecken brauchbaren Kalkspat in Frage kommen, schon seit längerer Zeit so
gut wie erschöpft sind, so macht es sich in den optischen Werkstätten der Mangel an
Kalkspat… immer mehr fühlbar.
-1924 Glaser, D…ein Umstand, der bei der heutigen Knappheit an gutem Kalkspat stark
ins Gewicht fällt.
-1925 Bouasse, Fr. book… D’où l’importance historique et technique de ce cristal don’t
les gros échantillons se vendent au poids d’or.
-1928 Schulz, D. in Wien-Harms ….ein in jeder Beziehung brauchbarer Ersatz für das bis
vor kurzem fast nur in Island in guter optischer Beschaffenheit geförderte Material
bislang noch nicht gefunden ist…..Die amerikanischen Vorkommen bei Cedarville
(Kalifornien) und Graycliff (Montana) liefern mit wenigen Ausnahmen nur
minderwertige…Kristalle. Weitere wenigstens bedingt brauchbaren Doppelspat
ergebende Fundstellen sind bekannt geworden in Südafrika, in Brasilien, sowie
neuerdings im Gebiet der russischen Sowjetrepubliken.
- 1928 Schönrock, D. Eine Zeitlang [L.K.: around 1920?] schien es allerdings, als wenn
bald die nötige Menge an reinem Kalkspat-Material nicht mehr geliefert werden könnte.
-1931 Coker and Filon, U.K. book …Of late years the supply <strong>of</strong> Iceland spar has not been
kept up, and <strong>of</strong> consequence new Nicol prisms are almost impossible to obtain….
-1933 Smith, U.K. (at Hilger Ltd.) It is becoming increasingly difficult, for example, to
obtain crystals <strong>of</strong> calcite which will enable first quality Nicol’s prisms to be made with a
maximum aperture <strong>of</strong> 1 in. diameter. In Smith’s U.S. Patent it is also stated that…pieces
<strong>of</strong> Iceland spar are no longer obtainable, at no matter what price, in sizes large enough to
cut prisms <strong>of</strong> more than 50 mm. effective aperture.
-1933 Lyot, Fr. mentions in a 1941 paper that his ingenious monochromatic filter which
needed 10 Nicol prisms (<strong>of</strong> Glazebrook-type, with 18-mm aperture) could not be
constructed “faute du spath nécessaire pour les tailler”. The filter was eventually made in
1938 with Polaroid sheets and in 1940 with Iceland spar.
- 1935 Hardy, U.S. Uses a specially designed calcite-glass Rochon prism instead <strong>of</strong> a
Nicol prism in his new spectrophotometer, partly to economize on calcite.
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