15.vii.'01
Hello,
For relatively up-to-date and complete information on osumilite,
including all optical properties, I heartily recommend the 2nd edition of
DHZ, vol. IB (1986), pp. 541-558. Forty-six references (through 1983) are given.
Having little relief and being uniaxial (+) with weak birefringence
{~0.005), osumilite could be confused with quartz. However, an experienced
petrographer would be unlikely to confuse the mineral with cordierite which
is biaxial and only rarely has a 2V smaller than 60 degrees.
Good luck!
Tomas Feininger
Petrographer
|