Suki, Just a few ideas.
This sounds like a plastic or composite sink. Americast is a common inexpensive composite sink that usually has to be professionally repaired & the expense is often not worth it, does it look like any of these:
http://www.showerbuddy.com/Showroom/Kitc..._sink.html
Some of the composites can be buffed out (Corian sinks are common seamless welded into the counter & can be buffed out)
I doubt that this was a cast iron /porcelain sink, as a match probably would not marr the porcelain....but it is easy to check, cast iron is magnetic.
Here is a check list of the different types of composites:
Composite
The use of composite kitchen sinks is growing rapidly, according to U.S. Department of Commerce statistics. But, because there are many types of composite sinks, there is much confusion in differentiating one from another. In general, there are three main types: polyester/acrylic, quartz composite and granite-based.
Polyester/Acrylic
Of all the types of composite sinks available, polyester/acrylic are the lowest performing in terms of scratch and stain resistance, as they are made from soft materials that can cut and nick easily.
On the positive side, polyester/acrylic based composites tend to have a "shiny" look, which appeals to many homeowners because they brighten up a kitchen. They are also popular because they come in a variety of colors. These composite sinks also have an affordable price for those who need to adhere to a strict budget.
Quartz Composite
With a combination of 70 percent quartz and 30 percent resin filler, quartz composite sinks provide a much more durable surface than do polyester/acrylic. These sinks can resist everyday cuts, scuffs and dents and can easily stand up to harsh cleaning materials or liquids that can stain other sinks.
Quartz composite sinks are available in a variety of colors. For example, MoenStone designer kitchen sinks come in a number of colors including dramatic options such as sapphire blue and a bright yellow stone. Since the color is uniform throughout, the material never loses its original color.
"Because of the durable surface, you can take a boiling pan right off the stove and set it in a MoenStone quartz composite sink without having to worry," explains Allison. "In addition, quartz composite sinks will fight thermal conductivity to keep dishwater warm longer."
At affordable prices (starting at $250), these composite sinks are available in many popular configurations such as big/medium bowls and many offer matching bar and preparatory sinks. Composite sinks can easily be mounted from either above or below the counter. The only drawback to this type of sink is that with some styles, consumers may give up some of the glossy finish that they would get from a cast iron sink.
Granite-Based
The most scratch resistant sink material on the market today is a "granite" composite. Already popular in Europe, these sinks are just making their way to the U.S. Although you might pay a premium price for these sinks, they offer extreme chemical and scratch resistance. These sinks offer the highest level of durability thanks to an extremely high density of rock particles at the sink's surface. Since granite-based sinks are only available in matte finishes, consumers who prefer a glossy look should explore other composite options.
Solid Surface
Solid surface sinks have become increasingly popular because of their ability to be one, integral unit with the countertop. This is an attractive option for those who want a clean surface with no exposed edges from countertop to sink.
There is a misconception though with solid surface sinks -- many think that solid surface materials are some of the hardest sink materials on the market, but in actuality they are softer than the quartz composite sink. The acrylic polymer composing the sink can nick, scratch and dent, but can be repaired. However, the repair process may be too difficult for a do-it-yourselfer and require a professional's visit.
Although they can be cost prohibitive for some, solid surface sinks do offer excellent resistance to heat and light exposure and are easy to maintain.
