Silica turning transparent during column chromatography with chloroform
You are correct, sir!  (or madame)  The silicic acid becomes translucent (not transparent) in chloroform because their refractive indexes are similar.  This is a chance to check for air bubbles in the column, which reduces efficiency.  Also, any material still on your column will probably not have the same RI, and will be visible as a white or colored band, probably at the top of the column.