
Obsidian possibly used in trephination experiments
1918-1920
1918-1920
1901-1930
1945
1945-1948
1880
1936
1869
circa 1900
circa 1915
1845-1855
1821
circa 1842
1858
1853-1857
1900-1920
1920-1950
c.1912
1934
1913
1949
1849
1925-1926
1901-1920
1884-1900
1920-1950
1822
1920-1950
1829
1925-1935
1890-1930
1847-1848
1879-1896
1829
circa 1900-circa 1948
1948-1950
1950
1888
1880-1900
before 1889
1870-1888
1886
1890 - 1900
1853
1938
1920
1865
1947
1938
1923-1948
1938