The pits in the surface of the glass come from a process called hydration. The soda and lime used in making the glass is leached out, leaving the small pits. Clear Sea Glass can come from many sources, old pop bottles, broken windows, even car & boat wind shields. Black Sea Glass is rarely found and often originates from pre - 1860 glass that is actually dark olive green, dark brown or purple. Almost non existent. Red Beach Glass, Very Rare may have come from ship signal lights, locomotive lanterns or car tail lights it is so rare because gold was actually used as the compound to turn glass red. Cobalt Blue - Many medicine bottles were cobalt blue glass. Kelly Green Beach Glass - Green Glass comes in many shades, from pop wine and beer botles. Beach Glass that been melted in a fire, becomes Fire Glass, the rarest of sea glass, and often has inclusions, things inside. These are often found near old dumps.