Natrolite, analcime, and thomsonite
are typically found as alteration products of mafic rocks, where they develop within late stage alteration assemblages [47, 90].
Figure 5k shows the occurrence of neddle-like crystals of thomsonite
along with botroidal and fibrous spheroidal Fe-oxyhydroxides A fibrous and reticulate aggregate which is transparent to translucent having a variety of colours ranging from white to yellow to reddish gray, can be attributed to levyne (Figure 5l).
crystals were described by Hibsch (1915) from a strongly vesicular facies of the highest lava flow at the base of Pusty vrch Hill (490 m a.s.l., NW of Dobranka).
is generally massive or fibrous, beige to off-white.
The paragenetic sequence of the zeolite mineralization at this locality is calcite(I) [right arrow] chabazite [right arrow] thomsonite
[right arrow] mesolite [right arrow] analcime [right arrow] calcite(II) [right arrow] illite.
Name: For the relationship to other members of the thomsonite
Not until some years later did I realize that I had misidentified scolecite as thomsonite
has been found as a rare mineral in the Bor pit.
[NaCa.sub.2] [Al.sub.5] [Si.sub.5] [O.sub.20] [cdotp]6[H.sub.2]O
Extinction Sign of Zeolite Angle, Degrees Elongation Natrolite 0 + Thomsonite
0 +/- Scolecite 18 - Mesolite 8 + A single crystal fragment was examined and found to have negative elongation and an extinction angle of at least 15 [degrees].
Turning finally to the zeolites, Carati lists just four: scolecite, thomsonite
, phillipsite and chabazite.