This data sheet was compiled by the Building Research Establishment (BRE). Where possible, data collected in earlier surveys has been used to help interpret the test results. The data sheet was compiled in September 1999 using the results of tests carried out to the proposed European Standards. The work was carried out by BRE as part of a Partners in Technology Programme funded by the Department of the Environment, Transport and the Regions and the Rare Stone Group and does not represent an endorsement of the stone by BRE.

General
The stone is mined near Teffont, close to the A30 in Wiltshire. The stone has a long history and was used extensively at Salisbury Cathedral. The maximum block size is 2700 x 1200 x 500mm.

Petrography 
The stone is a fine grained dense glauconitic limestone from the Portlandian formation (Jurassic). It is usuall a greenish grey colour.

Expected Durability and Performance 
It is important that the results from the sodium sulphate crystallisation tests are not viewed in isolation. They should be considered with the results from the porosity and water absorption tests and the performance of the stone in existing buildings. Stone from Chilmark has been used for many years in a wide range of locations. The low saturation co-efficient indicates a stone that will have good resistance to weathering. The crystallisation test results show the stone to be Class A which BRE Report 141 suggest is suitable for most uses and that it should have good resistance to both salt and frost. Based on current research it seems likely that the stone would weather at a rate of between 1 and 2 mm per 100 years but it could be greater in severe exposures or on the edges of stonework. The strength is at the top end of the range for limestones.

Test Results - Chilmark (Chilmark Mine)

Safety in Use
Slip Resistance (Note 1)	N.D.	Values > 40 are considered safe
Abrasion Resistance (Note 1)	N.D.	Values <23.0 are considered suitable for use in heavily trafficked areas
Strength under load
1) Compression(Note 2)	131.5 MPa	Loaded perpendicular to the bedding plane ambient humidity
2) Bending (Note 1)	N.D.	Loaded perpendicular to the bedding plane ambient humidity
	N.D.	Loaded parallel to the bedding plane ambient humidity
Porosity and Water Absorption
1) Porosity (Note 3)	7.6%
2) Saturation Coefficient (Note 3)	0.65
3) Water Absorption	1.97% (by wt)
4) Bulk specific gravity	2496kg/m3
Resistance to Frost
Freeze/Thaw Test (Note 1)	N.D.
Resistance to Salt
Sodium Sulphate Crystallisation Test (Note 3)	-0.20% Mean wt loss

(Test methods Note 1 = EN1341, Note 2 = EN 1342, Note 3 = EN 1341 /BRE 141, Note 4 = BRE 141, Note 5 = based on earlier BRE data)

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