Dark Gray Corundum Necklace (Gray Sapphire).
Corundum has two primary gem varieties: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present.
Many factors can influence the condition of jewelry. Therefore you should make sure that your jewelry is properly cleaned, repaired and stored.
Always protect your jewelry from water, knocks, scratches, chemicals, sunlight and heat/cold to minimize these effects.
Ideally, store your jewelry in its Coralia Leets soft lined box or pouch and try to keep pieces apart, so that they don't rub together or tangle up.
Take care to avoid extreme humidity or heat as this may cause tarnishing. This will keep them looking their best.