This is a sample of just over 20 grams of arsenic. The arsenic has a somewhat fern-like structure, with strongly knotted leaves. It is not shiny, but dark gray. The dark grey color is due to a layer of oxide, which makes the appearance dull. Commercial samples of arsenic usually look like this.

When the oxide layer is removed, then arsenic looks much more metallic and also more attractive. The picture below shows another sample of approximately 7 grams, which was briefly treated with a hot solution of potassium dichromate in dilute sulphuric acid. This treatment removes the oxide layer. After the treatment, the sample was rinsed well and quickly was transferred to a vial, filled with warm distilled water in which a small amount of sulphur dioxide is dissolved, so that it is not re-oxidized again. The vial is sealed and the arsenic remains under the water with sulphur dioxide dissolved in it. This sample shows the crystalline and metallic appearance of arsenic.

The picture below shows 500 grams of a commercial sample of arsenic, and appr. 90 grams of arsenic, which is cleaned with acidified potassium dichromate, as described above. This picture nicely demonstrates how arsenic becomes dull and dark, due to aerial oxidation. When this oxide layer is removed then the material looks grey metallic.

This is a very toxic element, and its compounds also are very toxic.