Visual Basic - Conocer PK

hay alguna propiedad del Recordset que me diga si determinado campo es PK (clave primaria)

Fijate con esto, es con ADOX, otra posibilidad es con OpenSchema de ADO:

Dim cnt As Connection, cat As Catalog, oIndex As Index, oColumn As Column

Set cnt = New Connection
cnt.Open "MiConnectionString"

Set cat = New Catalog
Set cat.ActiveConnection = cnt

With cat.Tables.Item("MiTabla")
For Each oIndex In .Indexes
If oIndex.PrimaryKey Then
For Each oColumn In oIndex.Columns
Debug.Print oColumn.Name
Next
End If
Next
End With