And here's what the Catechism of the Catholic Church maintains:
Envy is a capital sin. It refers to the sadness at the sight of oneself, even unjustly. When it wishes grace harm to a neighbor it is a mortal sin:
St. Augustine saw envy as "the diabolical sin." "From envy are born hatred, detraction, calumny, joy caused by the misfortune of a neighbor, and displeasure caused by his property. (St. Gregory the Great)
Envy represents a form of sadness and therefore a refusal of chairty; the baptized person whould struggle against it by exercising good will. Envy often comes from pride; the baptized should train himself to live in humility:
Would you like to see God glorified by you? Then rejoice in your brother's progress and you will immediately give glory to God. Because his servant could conquer envy by rejoicing in the merits of others, God will be praised. (St. John Chrysostom)
It has a lot more to say about the tenth commandment but I found the Augustinian roots of this section particularly scintillating. How challenging and refreshing to be told that inordinate desire, and/or consumption, is a form of sadness.