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A fossil can be studied to determine what kind of organism it represents, how the organism lived, and how it was preserved.
However, by itself a fossil has little meaning unless it is placed within some context.
Iron and other transition elements may give the obsidian a dark brown to black color. In some stones, the inclusion of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern (snowflake obsidian).
The inhibition of atomic diffusion through this highly viscous and polymerized lava explains the lack of crystal growth.
Obsidian is hard and brittle; it therefore fractures with very sharp edges, which were used in the past in cutting and piercing tools, and it has been used experimentally as surgical scalpel blades.
It is estimated to require four hours of class time, including approximately one hour total of occasional instruction and explanation from the teacher and two hours of group (team) and individual activities by the students, plus one hour of discussion among students within the working groups.
Explore this link for additional information on the topics covered in this lesson: This activity will help students to have a better understanding of the basic principles used to determine the age of rocks and fossils. Objectives of this activity are: 1) To have students determine relative age of a geologically complex area.It is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.