Sulphur - S8
This is a sample of so-called 'flowers of sulphur'. Chemically speaking, this is one of the purest forms of sulphur one can get, but it frequently contains small amounts of oxygen, which together with humidity may give rise to some acidity. For many chemical experiments this is of no concern, but it is a concern in some pyrotechnic mixtures.
Bulk sulphur is brighter yellow and has a clearly visible crystalline structure. The following picture shows a piece of approximately 25 grams of pure sulphur. It has a bright yellow color, but it is not shiny.