sion
of the peridotite is shown by the facts stated to be between Lower and
Upper Cretaceous. It seem reasonable to assume that the intrusion
accompanied diastrophic movements of this period, during which there
was a land elevation recorded by the unconformity noted.
INDIANA.
The
finding of another diamond in August, 1912, in Morgan County, Ind.,
again attracts attention to that region. This stone was found by F.
Doyle while panning for gold near the junction of Gold Creek and
Sycamore Creek. Through the kindness of Messrs. Perry Bradford and R.
L. Royse, of Centerton, Ind., the writer was afforded an opportunity to
examine this diamond and another smaller costal found in a previous
year. The larger stone weighs 2.28 metric carats. It is a distorted
flattened hexoctohedron with strongly curved faces. It is practically
colorless with a small dark chrome-green spot near the surface, which
gives the whole a slightly greenish cast in certain positions. If it
were desired to cut this diamond it would yield a fine gem with
probably very small waste. The other diamond weighs 0.135 metric carat.
It is an elongated clear light-brownish crystal with curved faces,
possibly also a hexoctohedron.
Probably
as many as 20 diamonds in all have been found in Morgan and Brown
counties during the last 35 years in panning and washing for gold. W.
S. Blatchley * mentions eight diamonds examined by himself and states
that" he had "credible information concerning several others. ' The
following notes are abstracted from Blatchley's report: The presence of
gold in the gravels of Morgan County has been known over 60 years and
was subsequently determined in numerous counties. Records show mining
was in progress in 1850, and since that time the gravels at a number of
localities have been washed intermittently. The earliest record of the
discovery of diamond in Indiana is a note by E. T. Cox2
mentioning a stone weighing 3 carats from Little Indian Creek, in
Morgan County, and the discovery of several diamonds in Brown County,
one of which weighed 4 carats. Of the eight diamonds seen by Blatchley,
the largest was the Stanley diamond, found in 1900 in a branch of Gold
Creek, Morgan County. This stone was an octohedron and weighed 4-7/8
carats. It had a peculiar greenish-yellow tinge with a black spot, not
quite central. It was cut into two stones weighing 1-1/8 and 1-1/16
carats, respectively. The other stones ranged from less than
one-eighth of a carat to 1-21/32 carats in weight and consisted of
dodecahedral and hexocto-hedral crystals of white, yellow,
brownish-yellow, bluish, and pink colors.
A
large variety of minerals and rocks are found associated with the gold
and are accordingly associates of the diamonds. The concentrates
obtained by the present writer from a deposit on Highland Creek, in
Morgan County, contain large quantities of black sands and pebbles,
composed of magnetite, hematite, titanic iron, pyrite or marcasite, and
small quantities of corundum, garnet, zircon, cyanite, etc. Bowlders in
the stream gravels consist of numerous basic rocks, as gabbro, diorite,
diabase, and amphibolite, and also of granite,
i
Gold and diamonds in Indiana: Twenty-seventh Ann. Kept. Indiana Dept.
Geology and Nat. Resources, 1902, pp. 11-47. ? Eighth, Ninth, and
Tenth Ann. Repts. Indiana Geol. Survey, 1878, p. 116.
