Propolis also called bee glue. is a resinous mixture that honey bees produce by mixing saliva and beeswax with exudate gathered from tree buds, sap flows, or other botanical sources. 
It is used as a sealant for unwanted open spaces in the hive.
Propolis is used for small gaps while larger spaves are usually filled with beeswax.
Propolis color varies depending on its botanical source, with dark brown as the most common.
Propolis is sticky at the above 20?, while at lower temperatures, it becomes hard and brittle.

Chemical analysis
heavy metal ≤ 10.0mg/kg
Pb ≤ 2.0mg/kg
As ≤ 1.0mg/kg
Hg ≤ 0.1mg/kg