Black streaks

In the nailbed, a black streak or wide variegated brown streak, elevation of nailbed, skin next to nail becomes darker, nail looks deformed or is being destroyed size of nail streak increases over time. 

Pigment agglomerates, stagnant Black streaks or specks 11.12.2... 

As discussed in Section 11.12.2, several root causes exist for black streak contamination in molded parts. These root causes include degradation of the resin in the screw channels and nonreturn valve or runner system, degraded material entering with the resin feedstock, and poorly dispersed pigments in the color masterbatch. To determine if the color concentrate masterbatch was the source of the black streaks, the color concentrate was removed from the feedstock and only natural... 

As previously mentioned, plant personnel were successful at mitigating the black streaks with the use of static mixers positioned inside the injection nozzle. Since the degraded resin was soft and leathery, it was easily broken into smaller particles as they passed through the mixer. Thus, the particles were not eliminated they were just reduced in size such that they did not create as many black streaks. The additional pressure and time that was required to inject the resin through the static mixers and into the mold, however, increased the cycle time to an unacceptable level. Although static mixers can be used to mitigate these types of problems, they do not eliminate the root cause of the degradation problem. 

Fig. 11. Simulation of the physical model by means of two sources of Marangoni effect generation. The upper phase is paraffin oil and the lower phase is ethylene glycol. Through the two capillaries (the two vertical black streaks) ethyl acetate is fed.

A few years ago it was pointed out to me by Sterling Hendricks that ordinary black mica, biotite, which has an intensely black color, owes this color to the presence of iron in both the ferrous and ferric oxidation state. Black tourmalines also usually contain both ferrous and ferric iron. Another intensely black mineral, with black streak, is ilvaite, with composition Ca(Fe )aFe+++(Si04)20H. 

Grayish-black to steel-blue, brittle, or fibrous pieces producing a black, or grayish-black, streak. The preparation contains about 90 per cent of Mn02. 

STEPHANITE. The mineral slephanite. silver antimony sulfide, Ag5-ShS7, is found in short prismatic or tabular orthorhombic crystals. It is a brittle mineral hardness, 2-2.5 specific gravity, 6,25 metallic luster culor, black streak, black opaque. 

Iron pyrites, pyrite, marquisite, or mundic is the name given to a brass-coloured sulphide of iron to which the formula FeS2 is usually ascribed. It often occurs in coal, and is known by miners as brass or fool s gold. The spontaneous combustion of coal is frequently facilitated by the oxidation of iron pyrites to iron sulphate.6 It often crystallises in cubes, the faces showing striations but a very characteristic form is the pentagonal dodecahedron, usually termed the pyritohedron. Hardness 6 to 6-5 density 4 8 to 5-2. It leaves a greenish or brownish-black streak. 

Cobalt-nickel pyrites, (Fe, Co, Ni)Sa, has been found in Westphalia as small cubic crystals, steel-grey in colour, giving a greyish-black streak.3 Density 4 7, hardness 5 to 5 5. Iron nickel pyrites, (Fe,Ni)S2, occurs in Norway 4 and in the Sudbury district, Ontario.5... 

Lolingite, FeAs2, occurs in Saxony and Norway in rhombic crystals. Hardness 5 to 5 5 density 6-8 to 8 7. Greyish m colour, it gives a greyish black streak. When heated in an open tube a white sublimate of arsenious oxide or white arsenic S5 is obtained in the absence of air metallic arsenic is volatilised to a dark sublimate. 

Cannel coal is a dull, compact, bituminous coal, that is to say it is rich in volatile hydrocarbons and bums very easily. It consists of varied plant debris, and under magnification it can be seen that it is made up of spores. It is brittle with a slightly paler sheen than that of jet and does not take such a high polish. It has a conchoidal fracture but produces a black powder when worked. It was more commonly used for large pieces than for jewellery. It leaves a black streak when mbbed against a matt surface such as unglazed porcelain. 

Anthracite is very black, but it is britde and has a glassy appearance. It can be successfully made into small items and was used in America for this purpose at the turn of the twentieth century. It gives a black streak. 

Shellac was a substance excreted by insects. It was mixed with wood flour, moulded and dyed - usually black or brown. It was lifter Than bois duici and gave good detail in moulding. It was used to make picture flames (F. 13.1), dressing table sets, some jewellery and, notably, 78 tpm gramophone records. Examined under a microscope it is possible to see the wood content. Black shellac gives a black streak. 

Celluloid was one of the early plastics that was used in numerous ways. It was made of cellulose nitrate and was extremely combustible, but a safer version, cellulose acetate, was later developed. Dyed black, they are reasonable imitations of jet but th have a plasticy look and feel. Black celluloid gives a fldnt, black streak. Baikelite, or phenol formaldehyde, could be dyed any colour and was widely used. When dyed black, it was also a reasonable jet imitation, but it dulls with age and has a plasticl look and feel. Black Bakelite gives a black streak. 

Root rot causes reddish black streaks on the roots plants are stunted and yellow. Cool, wet soil encourages this fungal disease. Destroy wilted plants. Replant with fresh seed in well-drained, warm soil. Soak seed in compost tea before planting. 

Leaves with black streaks filled with dark brown powder. Cause Smut. Young plants are usually affected. Cool soil makes plants more prone to this fungal disease. Warm soil by covering it with clear plastic for a few weeks before you plant. Prevent problems by planting tolerant cultivars such as Evergreen Hardy White and Tokyo Long White. ... 

Plant yellows, wilts, and dies. Cause Bacterial wilt. The stems have black streaks, and roots will rot. There is no cure. Avoid... 

Properties Black mineral, black streak, submetallic or dull to metallic luster. Contains 72.4% iron. Readily recognized by strong attraction by magnet. Soluble in powder form in hydrochloric acid. Decomposes at 1538C to ferric oxide Fe203, d 4.9-5.2, hardness 5.5-6.5. 

Properties Bluish-gray color, gray-black streak, metallic luster. One perfect cleavage, greasy feel. Mohs hardness 1-1.5, d 4.6—4.8. Similar in appearance to graphite. Soluble in sulfuric and concentrated nitric acids. 

Properties Black color, brownish-black streak, pitchy to dull luster. Mohs hardness 5.5, d 6.5-8.5. 

Properties Brass-yellow or brown, tarnished mineral, greenish or brownish-black streak, metallic luster. D 4.9-5.2, hardness 6-6.5. 

---