Iron ocher

Brauneisen, -erz, n., -mulm, m. Brauneisen-stdn. -ocker, m. brown iron ocher, atMn, m, brown iron ore, limom te. 

Roteisen-erz, n. red iron ore (hematite), -ocker, m. red iron ocher (earthy hematite), -stein, m. — Roteisenerz. 

The residue after sulfur distillation contained all the iron from the pyrite and also much sulfur. It was heaved out onto pot mountains and weathered there for twenty years. In this process two layers were formed - one lower, hard and salty one upper, loose as mold. The lower was iron(ii) sulfate, from which iron vitriol was prepared for use in textile dyeing. The upper layer contained iron oxide hydrate FeOOH, iron ocher, and was the raw material for the manufacture of red ocher paint. During the weathering processes in the pot mountains, sulfur dioxide was evolved, evilsmelling but disinfecting. In periods of plague in the country, prominent persons, such as those from the King s court in Stockholm, arrived at Dylta for protection on or near the pot mountains. 

Iron Oxides. In addition to the black iron oxide, there are several natural and synthetic yellow, brown, and red oxides. As a class, they provide inexpensive but dull, lightfast, chemically resistant, and nontoxic colors. The natural products ate known as ocher, sieima, umber, hematite, and limonite. These include varying amounts of several impurities in particular, the umbers contain manganese. Their use is limited because of low chroma, low tinting strength, and poor gloss retention. 

Ochers and siennas Natural earths, mixtures of silica and iron oxides... 

Pigments are classified as organic or inorganic. Organic pigments are brighter, less dense, and smaller in particle size than the more widely used, more opaque, inorganic colorants. Iron oxides or ochers are available as yellow, red, black, brown, and tan. 

Pyrite, Green Vitriol, and Ocher. In 1579 Matthias Falconer of Brabant founded at Queenborough the first plant in England for converting iron pyrites into copperas (ferrous sulfate, or green vitriol) and... 

Goethite is the colored component of yellow ocher a weathering product mainly of siderite, sulfidic ores, and feldspar. It occurs in workable amounts mainly in the Republic of South Africa and France. The Fe2Oa content gives an indication of the iron oxide hydroxide content of the ocher, and is ca. 20% in the French deposits and ca. 55% in the South African. 

Natural iron oxide pigments are mostly used as inexpensive marine coatings or in coatings with a glue, oil, or lime base. They are also employed to color cement, artificial stone, and wallpaper. Ocher and sienna pigments are used in the production of crayons, drawing pastels, and chalks [3.5]. 

Umontte. mtncralogically composed of various mixtures of the minerals goethtte and lepitlttcrotite. HFcO- and FeOlOH). respectively. Goelhitc contains 62.961 Fe. Hie. () . and 10.15F HsO. sp gr 3 6-4.0. conmumly yellow or brown to nearly black, compact to earthy and ocherous. I.itnoniles are important sources of iron throughout the world. 

Iron oxides are supplied to the market as red, ocher, sienna, and umber natural pigments. The hue of the natural iron oxide pigments is determined by raw material composition and processing. 

The infrared spectrum of the iron oxide (Figure 19) used to simulate ocher displays distinctive absorbance bands in the region of 537 cm-1 and 465 cm-1. Not only are the bands obvious in fibers pigmented with iron oxide, but the rabbit hair which had been colored with the pigment retained evidence of that pigmentation even when it was charred (Figure 20). 

Ocher is a weak tinting agent and is often replaced by synthetic hydrated yellow iron oxides for brighter color and better uniformity. 

Some simple oxides are brighdy or strongly colored, and have been used as pigments. This includes the common oxides of iron, hematite, which is red and black, and goethite (syn. limonite), which is yellow or brown. These compounds have also been called ocher, yellow ocher, or brown ocher. Minium and massicot... 

Derivation Indefinite mixture of iron oxide and organic matter. Obtained from bog-earth, peat deposits, or ochers that contain bituminous matter. 

Iron Oxide Pigments. The discovery of iron oxide pigments is lost in antiquity. The cave paintings of early man were made with earth colors composed of iron oxides. Even today, natural iron oxides are still in use. The yellows such as the yellow others and siennas are hydrated ferric oxides (Fe203 H20). The nonhydrated ferric oxides (Fe203) comprise the reds and browns such as the red ochers and brown umbers. The blacks are mixed ferrous and ferric oxides (Fe304 or more precisely Fe0 Fe203). 

A brown earth that is darker in color than OCHER and SIENNA because of its content of manganese and iron oxides and is highly valued as a permanent PIGM ENT either in the raw or CALCINED state. 

---