Ochre - online puzzles

Online puzzle Ochre

Ochre (British English) ( OH-kər; from Ancient Greek: ὤχρα, from ὠχρός, ōkhrós, pale) or ocher (American English) is a natural clay earth pigment which is a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colours produced by this pigment, especially a light brownish- yellow. A variant of ochre containing a large amount of hematite, or dehydrated iron oxide, has a reddish tint known as " red ochre" (or, in some dialects, ruddle).

The word ochre also describes clays colored with iron oxide, derived during the extraction of tin and copper.

Earth pigments

Ochre is a family of earth pigments, which includes yellow ochre, red ochre, purple ochre, sienna, and umber. The major ingredient of all the ochres is iron (III) oxide-hydroxide, known as limonite, which gives them a yellow colour.

Yellow ochre, FeO(OH)·nH2O, is a hydrated iron hydroxide (limonite) also called gold ochre.

Red ochre, Fe2O3, takes its reddish colour from the mineral hematite, which is an anhydrous iron oxide.

Purple ochre, is identical to red ochre chemically but of a different hue caused by different light diffraction properties associated with a greater average particle size.