From BiblePortal Wikipedia

King James Dictionary [1]

VEIN, n. L. vena, from the root of venio, to come, to pass. The sense is a passage, a conduit.

1. A vessel in animal bodies, which receives the blood from the extreme arteries, and returns it to the heart. The veins may be arranged in three divisions.  1. Those that commence from the capillaries all over the body, and return the blood to the heart.  2. The pulmonary veins.  3. The veins connected with the vena portarum, in which the blood that has circulated through the organs of digestion, is conveyed to the liver. 2. In plants, a tube or an assemblage of tubes, through which the sap is transmitted along the leaves. The term is more properly applied to the finer and more complex ramifications, which interbranch with each other like net-work the larger and more direct assemblages of vessels being called ribs and nerves. Veins are also found in the calyx and corol of flowers.

The vessels which branch or variously divide over the surface of leaves are called veins.

3. In geology, a fissure in rocks or strata, filled with a particular substance. Thus metallic veins intersect rocks or strata of other substances. Metalliferous veins have been traced in the earth for miles some in South America are said to have been traced eighty miles. Many species of stones, as granite, porphyry, &c. are often found in veins. 4. A streak or wave of different color, appearing in wood, marble, and other stones variegation. 5. A cavity or fissure in the earth or in other substance. 6. Tendency or turn of mind a particular disposition or cast of genius as a rich vein of wit or humor a satirical vein

Invoke the muses, and improve my vein.

7. Current.

He can open a vein of true and noble thinking.

8. Humor particular temper. 9. Strain quality as my usual vein.

Webster's Dictionary [2]

(1): ( n.) Peculiar temper or temperament; tendency or turn of mind; a particular disposition or cast of genius; humor; strain; quality; also, manner of speech or action; as, a rich vein of humor; a satirical vein.

(2): ( n.) A train of association, thoughts, emotions, or the like; a current; a course.

(3): ( n.) A streak or wave of different color, appearing in wood, and in marble and other stones; variegation.

(4): ( n.) A narrow mass of rock intersecting other rocks, and filling inclined or vertical fissures not corresponding with the stratification; a lode; a dike; - often limited, in the language of miners, to a mineral vein or lode, that is, to a vein which contains useful minerals or ores.

(5): ( n.) A fissure, cleft, or cavity, as in the earth or other substance.

(6): ( v. t.) To form or mark with veins; to fill or cover with veins.

(7): ( n.) One of the vessels which carry blood, either venous or arterial, to the heart. See Artery, 2.

(8): ( n.) One of the ribs or nervures of the wings of insects. See Venation.

(9): ( n.) One of the similar branches of the framework of a leaf.

International Standard Bible Encyclopedia [3]

vān  : Only in   Job 28:1 , the King James Version "a vein for the silver," or מוצא , mōcā' , "going forth," "source." Both the King James Version "vein" and the Revised Version (British and American) "mine" are more specialized than mōcā' , but the Revised Version (British and American) doubtless conveys the original meaning.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [4]

( מוֹצָא , Motsa, a Source, as often), a Mine (q.v.), as of silver ( Job 28:1).