In 1832 the Garnkirk Fireclay Company (known originally as the Garnkirk Colliery and Brickfield), owned by Mark Sprot of Garnkirk House and his brother and let to James Murray & Co., was established in the vicinity of the railway at Garnkirk. It was reputed to be one of the largest and most complete works in the United Kingdom, using a bed of fireclay 4 to 19 feet thick, of a composition superior to that used elsewhere in the trade. The products were therefore of a high standard, the fireclay bricks, ornamental vases, urns, etc., being highly sought after. It is recorded that in addition to an "immense wholesale home trade" there were exports to France, Germany, Russia, the East and West Indies, U.S.A., and New Zealand. In 1869 300 men and boys were employed, and 200 tons of clay and about an equal weight of coal were being used daily. There was an internal railway system, which had earlier extended to limestone pits in the Crowwood area and to fireclay workings in the Woodhead locality. The fireclay pits were finally exhausted in 1895 but the works continued in production until 1901, when the buildings were advertised for sale.

In 1833 the clay deposits owned by Dr James Jeffray of Cardowan House came into use, on the formation of the Heathfield Fireclay Works of Peter Ferguson & Co., later Ferguson, Miller & Co., who continued in charge until about 1862. In the years following there were changes in ownership. 
Trading continued under the name of Heathfield and Cardowan Fire Clay Co. and the works were considerably extended. The output over the years was varied and included firebricks, tiles, ornamental vases, chimney pots, sewerage pipes and the like. The firm continued into the late 1960s and just prior to that time about 100 men were employed. 

Kilns at Heathfield Fireclay Works  

The works were in time demolished as were the nearby houses of Heathfield village where some of the workers resided. In addition to the lime pits in the area of Garnkirk and Crowwood, there were also deposits of hard blue lime on parts of the Bedlay estate. This was extensively used in the Monklands iron works.  

The Heathfield area is once again being occupied.  Heathfield Grange is a new housing estate built near the site - on land that was once part of the Garnkirk estate.