
          In the parcel you will find a fragment of the mineral which Prof. Del Rio
calls a carbonate of tellurium coloured by nickel. I have examined it, but
cannot find any selenium in it. It appears to be only a silicate of zinc,
coloured by copper. A similar mineral is said to occur in "Rutland Coal 
Mine, near Matlock, Derbyshire" (Phillips) Will you ask Mr. Shepard to
see whether the foreign variety occurs in the Gibbsian Cabinet & if it
does to compare it with this small specimen.

I found no proof sheets of your chemical work, on my return
nor have any been yet reviewed. It will give me pleasure to
examine them when they arrive.

With respect and esteem. I remain
my dear Sir
Your truly,

J. Torrey

Dr. J. Torrey
Oct 6th 1830
        