Jadeveon Clowney -- Baller Jewelry Run ... Day of the Draft

Jadeveon Clowney blinged himself out just hours before the NFL Draft -- dropping some NFL-style cash on incredible jewelry ... including gold necklaces, diamond pieces and a Rolex watch ... TMZ Sports has learned.

We know ... Clowney hit up Gabriel Jacobs from Rafaello & Co. in New York on Thursday and treated himself to some top quality items including:

-- 24k gold necklace with 10 ounce gold bar surrounded in a frame peppered in diamonds (estimated value: $20k)
-- Presidential Rolex watch with black face (estimated value: $45k)
-- Gold angel pendant with diamonds (estimated value: unknown but expensive)

Sources connected to Clowney tell us he also bought gifts for family members and people in his camp. We're told Clowney didn't want to be flashy, but rather "classy."

Clowney isn't the only baller who hit up Rafello & Co. that day -- a bunch of other NFL Prospects went jewelry shopping including:

Greg Robinson (#2 pick) All-black diamond Phantom Rafello Tourbillon watch
-- estimated cost: $123k

Khalil Mack (#5 pick) 18k Gold Cartier Santos XL watch
-- estimated cost: $84k

Mike Evans (#7 pick) Rolex Deep Sea Covered Watch (all VVS-quality diamonds) and custom diamond bracelet
-- estimated cost: $43k

Brandin Cooks (#20 pick) White gold & diamond Presidential Rolex watch
-- estimated value: $46k

Ha Ha Clinton Dix (#21 pick) All diamond Presidential Rolex and Cuban Link diamond bracelet with diamnod studs
-- estimated value: $55k

Johnny Manziel (#22 pick) Rose gold Presidential Rolex
-- estimated value: $30k