How to store a collection of floats in postgres?

Question

I'm building a script that saves tweets to a postgres database using ruby/pg/ActiveRecord/TweetStream (gem).

This script works fine..

...

TweetStream::Client.new.track(SEARCH_TERMS) do |t|
  puts "#{t.text}"
  attributes = {
    tweetid: t[:id],
    text: t.text,
    in_reply_to_user_id: t.in_reply_to_user_id,
    in_reply_to_status_id: t.in_reply_to_status_id,
    received_at: t.created_at,
    user_statuses_count: t.user.statuses_count,
    user_followers_count: t.user.followers_count,
    user_profile_image_url: t.user.profile_image_url,
    user_screen_name: t.user.screen_name,
    user_timezone: t.user.time_zone,
    user_location: t.user.location,
    user_lang: t.lang, 
    user_id_str: t.user.id,
    user_name: t.user.name,
    user_url: t.user.url,
    user_created_at: t.user.created_at,
    user_geo_enabled: t.user.geo_enabled,
  }
  if StoreTweet.create(attributes)
    puts "saved"
  else
    puts "error"
  end
end

until I add

user_geo_enabled: t.user.geo_enabled,
coordinates: t.coordinates.coordinates,}

I also tried

t.coordinates
t.coordiantes[:coordinates]
t[:coordinates] #this allows me to save but is always blank if when geo_enabled is 'true'

Twitter dev center (https://dev.twitter.com/docs/platform-objects/tweets) tells me that 'coordinates' is a collection of floats like:

"coordinates":
{
  "coordinates":
  [
    -75.14310264,
    40.05701649
  ],
  "type":"Point"
}

for the moment i use a 'text' field. Which type should i give to the field in order to store both values together?