In the Parashara Smriti, there is a verse which instructs to keep a black cat and precious stone in homes.
One should keep in his house the following things : the wood for striking out a sacrificial fire, a black cat, sandal-wood, a precious stone, ghee, sesamum seed, a skin of a black antelope and a goat. [Parashara Smriti 12.49.]
But Skanda Purana says keeping some animals like dogs, cats etc., as pets is not recommended and people who keep them reach hell.
One who keeps cats, cocks and hens, dogs and birds, one who sets fire to the houses of the deaf and blind as well as grasses and grains and other things in the fields and one who sustains himself by means of stagecraft and stellar calculations(astrology) - all these men go to Vaitarani. [39.18-20]
So, I think Parashara is not recommending us them to keep but not as pets.
The former verses in the smriti speak about the duties of a householder and the sacrifices.
A person who preserves his sacred fire, a tawny cow, a person engaged in offering a sacrifice, a king, a religious mendicant, and the great ocean, — the very sight of these purifies one ; therefore one should constantly obtain a sight of them. [Parashara Smriti 12.46]
Observing the former verses, verse 47 might also speaking about the things required for a sacrifice or used in a sacrifice.
Wood for striking out a sacrificial fire - used for striking sacred fire.
Sandal wood - This is also used as firewood.
Sesame seeds, Ghee - Used as offering in sacrifices.
Skin of a black antelope - Used by sages while performing meditation and used in some Yagnas.
Goats - They were used as an offering in sacrifices. Goats are also called as Aja. There is also another interpretation to the word Aja as vegetable seeds.
If the above interpretations are correct, then black cats and precious stones should have some importance in Yagnas.
There is an Agni Purana verse which says it is a good omen when a cat crosses one's path (from right to left) is in fact considered a good omen. (I couldn't understand why right to left is said here?!)
Good Omens: Good omens while leaving house are facing white flowers, full vessels, meat, distant sounds, goat, cow, horse, elephant, fire, gold, silver, sword, umbrella, fruits, butter or curd, sugarcane, sound of thunder, lightning, dead body without anybody crying, donkey’s braying; buffallo crossing from left to right; horse, cats, donkeys, from right to left.
The Agni Purana verse says cats are a good omen from right to left generally and doesn't specify black cats. Moreover, an omen is an event which happens coincidentally without our involvement.
Is there any commentary on Parashara smriti which explain these verses about importance of a black cat and precious stones in a sacrifice or any other use for a house holder?