Is this chain solid gold or plated?

It is solid 14k rose gold, stamped 14K, not a plated or gold-filled chain. That means the color runs through the metal rather than sitting on the surface.

Can it hold a heavy pendant?

At 1.1mm wide and about 1.7 grams, it is a fine chain. It handles small, light pendants well, but a heavy or large pendant can stretch or kink the cable links.

How long is it and where does it sit?

It is 16 inches long, which sits at the base of the neck for most wearers. That is shorter than the 18-inch length many pendants are styled on.

What clasp does it use?

It has a lobster clasp, which is more secure than a spring ring and easier to work one-handed.

Will rose gold match yellow or white gold jewelry?

Rose gold has a warm pink-copper tone. It layers well with yellow gold and looks distinct against white gold or silver, so it works best if you like mixed-metal looks.