Slag Glass
Slag glass is defined as colored, opaque glass wih an altenate color swirled throughout giving the appearance of marbling. For this reason it is sometimes called marble or malachite or mosaic glass. Popular colors include butterscotch, green and purple. The name has been used by glass-makers only in recent times and is derived from the belief that the colors were acheived by adding “slag” from iron smelting works to the glass.
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