So, let's clear some points up.
Iron is said in folklore to protect against a wide range of spirits and negative magics including [most of] the Good Neighbors and Alfar, Ghosts, Demons, and witches. Iron objects deter the majority of the Other Crowd who are averse to its presence and things like knives, scissors, nails, and horseshoes were recommended as protective objects. It is said that cemeteries had iron fences to contain any ghosts inside. Similarly older folklore said that demons were also repelled by iron, and it was believed to break the magic of witches. A horseshoe hung up above a doorway kept out a wide range of spirits as well as protecting from baneful magic.
Many people are familiar with the term 'cold iron' and associate it today with pure or simply worked forged iron - what is technically called 'pig iron' or 'crude iron'. Historically the term cold iron was a poetic term for any iron weapon and is synonymous today with the term 'cold steel'. So when you see a reference to cold iron it is talking about an iron weapon, usually a sword or knife.
As to iron and steel - they are effectively the same substance and have been treated that way in folklore and for apotropaic purposes historically. Steel is between 90 and 98% iron depending on the alloy, so a steel object is obviously mostly an iron object.
Those who are seeking to encourage the presence of the Gentry should remember their dislike of iron and limit its presence. On the other hand those seeking protection from Otherworldly influence would do well to keep iron or steel objects around. Remember though that I said earlier it is a protection against *most of* the Good Neighbors. In folklore there are some Fae it is known to have no effect on, including Etins, Redcaps, and spirits associated with mines or forges. Other protections are required for those, like salt or silver.
*editing to add:
in my experience iron ore and stones with high iron content work the same as iron, but to a weaker degree, ie hematite which is about 70-ish% iron and magnetite (72% iron) both work to deflect negative magic and to deter ghosts, negative spirits, and the Fey who are sensitive to iron but not as intensely as worked iron (even so-called 'pig iron').
Iron ore is most often hematite or magnetite along with a few others with a slightly lower iron content so it makes sense that they work in a similar fashion to iron. A variety of crystals also have iron as a component which is what give them their color, such as peridot, but usually not in an amount that would act as an effective deterrent (although I think its unlikely any Fey would wear them or desire to be around them and if you offer crystals to the Other Crowd I might suggest looking for ones without iron content)
- M. Daimler, 2016
