Have you ever come across what appear to be white flakes floating in your bottle of wine? The result is similar to a snow globe. Or perhaps the cork has crystalized? Did you assume that this somehow meant the wine was flawed or ruined?
Video courtesy of Dr. Vino
What you had most likely seen are tartaric crystals, commonly referred to as "wine diamonds."
Tartrate crystals are not uncommon for wines that are minimally filtered. Mass market wines will usually be treated to minimize crystal and sediment precipitation. Tartrate crystals are colorless and add no flavor to the wine (in fact Crème de Tartar is used in cooking as a thickening agent), but can as you noted, cause the wine to be gritty. Here are a couple of things that should mitigate (not eliminate) this issue. First and foremost, we frequently recommend that wines purchased from any winery and shipped via a package express company be laid down and left to rest for 4 to 5 weeks. That will allow any sediment (or tartrate crystals) to settle to one side of the bottle. Then when you are ready to enjoy your rested wine, carefully decant the wine into a decanter, leaving perhaps an inch of wine in the bottom of the bottle. The shape of the bottom of most Bordeaux and many Burgundy bottles have a punt at the bottom, designed in part to help capture the sediment.
Those two steps: letting the wine rest after its bottle shock from travelling, and decanting the wine should minimize the appearance of sediment and tartrate crystals.