DUALITY: Feminine (Hotaru is a girls, right?)
TRIPLICITY: Earth (Tomoe can mean "from earth")
RULING PLANET: Saturn (hum hum)
SYMBOL: The Goat (well.. uhh... no link with Hotaru)
DOMINANT KEYWORD: I Use (I use my silence Glaive)
KEYWORD: Self-mastery (I'm the master of what I can destroy)
LUCKY NUMBERS: 2 & 8 (8-2=6, Hotaru's birthdate)
LUCKY DAY: Saturday (Saturn = Saturday)
BIRTHSTONE: Garnet (OH!! See Mix)
CITIES: Oxford, Boston, Brussels, Chicago, Montreal (Hum.. it is based on
what all that? No matter. I'm Capricorn and I'm from Montreal!!!)
COUNTRIES: Mexico, Afghanistan, Bulgaria, India (same thing??)
FLOWERS: Carnation, Ivy, Tulip (when she bring a flower pot for Chibi-Usa,
it looks like a Tulip, isn't it?
METAL: Lead (in the manga #16, she's is the one who feels the arrival of Sailor Lead crow)
POSITIVE QUALITIES:
determination, dependability, stability, sureness, tranquility, wisdom (it's Hotaru herself)
NEGATIVE QUALITIES:
depression, loneliness, ruthless ambition, snobbery, selfishness,
narrowness, rigidity (it's also Hotaru!!)
LIKES: communing with nature,  interesting informative communication, history and  historical places, antiques, business, success, money in the bank, financial security. (antique = collecting lamps and history is her favorite course)
STONES: Jet, Onyx (no fluorite??)
COLOURS: Black, Grey, Violet (it's Hotaru's colours!!!!!!)

"Many astrologers acknowledge that Capricorn is the most difficult astrological sign to characterize, finding wisely varying types born under it. Yet it seems that Capricorns all share Saturn's sense of fatalism, which grants them a sort of acceptance very different from, for example, a joyful Aquarian openness. Capricorn admits trial, difficulty, even suffering to be part of life's package. Perhaps Capricorns are most suspicious when things seem too easy or to be going too well. Furthermore Capricorns will generally be accepting of the role they are to play in life, but can also lack the flexibility needed to change.

Capricorns have an instinctive knowledge of power and how it works. Many must beware of a tendency toward dictatorial behavior. Other Capricorns, however, do not specialize in telling people what to do, but how to do it; not infrequently they can demonstrate an impressive depth of knowledge to back up their statements. "

Sources:
http://www.nanceestar.com/CapricornEss.html
http://www.geocities.com/Paris/LeftBank/4423/cap.htm
http://home.earthlink.net/~sng/capricorn.htm
http://www.way.com/~thanos/divination/961209/capricor.htm
http://piglet.cc.utexas.edu/~ifin353/cap.html