In general, the soil is light-colored soft sand, nearly pure silica.

I found also a piece of palm-tree transformed into oxide of iron, and the pores filled with pure silica.

Of course, it isn't pure silica, because sand deposits like that don't exist, but it's so near it's unbelievable.

I suppose white silver sand, sold for cleaning harness, etc., is nearly pure silica, but what am I to do for alumina?

Dr. Turner found the ignited Indian tabasheer to consist almost entirely of pure silica with a minute quantity of lime and vegetable matter.

We also estimate that the n(2) of germania is three times the n(2) of pure silica.