The bar portion of the brooch is brownish black, with grain lines consistent with bog oak, horn, or tortoiseshell.  I’ve not been able to determine with certainty the material of the bar pin based on published characteristics of all materials mentioned above.  As seen in the photos, one end is translucent, ruling out bog oak.  Horn and tortoiseshell can be translucent and my opinion is that one of these two are the most likely to compose the bar portion.  The crape stones are jet black and are likely glass, or “French Jet”.

This wonderful old mourning pin measures 2 ¼” wide and ½” high.  Unsigned.