The calcined limestone is divided, according to its action in slaking and setting, into the following classes: -

1. Rich, Fat, or Pure Limes.

2. Poor Limes.

3. Hydraulic Limes.

4. Cements .Natural. Artificial.

These classes merge gradually the one into the other, without sharp distinctions, the difference between them depending upon the nature and amount of the foreign constituents associated with the lime, and upon the degree of calcination to which the stone has been subjected.

The physical characteristics of the raw stone are no index to the properties of the lime or cement produced from it. These properties may however be inferred from the nature and proportions of the chemical constituents of the stone. A general composition has been assigned to the materials yielding each of the classes above mentioned, but it must be borne in mind that this is only an approximate indication of quality, and that the behaviour when calcined and treated with 'water is the only safe means of classification.

The following Table shows the composition of a number of limestones and cement stones, chosen as characteristic examples, and intended to give some idea of the varieties actually met with.

In comparing these analyses with others, it must be borne in mind that these show the composition of the raw stone, or raw material from which the lime or cement is produced. Analysis of the burnt lime or cement would in each case have given a higher percentage of clay and sand, and the lime and magnesia would not appear as carbonates. (The carbonic acid would have been expelled during calcination.)

1 Magnesium carbonate.

Table Giving The Composition Of Various Limestones, Cement Stones, Etc., Before Calcination

Composition of Raw Stone or Raw Material.

Nature of Lime or

Cement produced.

Description.

Carbonate of Lime and Carbonate of Magnesia.

Clay, Sand, Iron, etc.

Water and

Loss.

Analyst or Authority.

Rich or Fat Limes.

Carrara Marble (see p. 55)

100 carb. lime

••

..

Vicat.

White Chalk .

98.6 carb. lime .4 carb. magnesia

99.0

2 iron, manganese and phosphates •8 silica and alumina

1.0

..

Schweitzer (Reid).

Bath Oolite (see p. 59)

94.5 carb. lime 2.5 carb. magnesia

97.0

l.2 iron and alumina 1.2

1.8

Professors Daniel and Wheatstone; Commission on Stone for Houses of Parliament.

Portland Oolite (see p. 60)

95.2 carb. lime 1.2 carb. magnesia

96.4

•5 iron and alumina 1.2 silica

1.7

1.9

Do.

Poor Limes.

Siliciferous Oolite, Chilmark Stone (see p. 63)

79.0 carb. lime 3.7 carb. magnesia

82.7

2.0 iron and alumina 10.4 silica (nearly all sand)

12.4

4.2

Do.

Feebly

Hydiaulic.

Grey Chalk, Hailing (see p. 155)

92 carb. lime .

8 clay .

..

Col. Scott, R.E.

Hydraulic.

Roach Abbey, Dolomite (see p. 59)

57.5 carb. lime 39.4 carb. magnesia

96.9

.7 iron and alumina .8 silica

1.5

1.6

Professors Daniel and Wheatstone; Commission on Stone for Houses of Parliament.

Bolsover, Dolomite (see p. 59)

51.1 carb. lime

40.2 carb. magnesia

91.3

1.8 iron and alumina 3.6 silica

5.4

3 3

Do.

Carboniferous, Aberthaw (see p. 155)

86.2 carb. lime

11.2 clay .

2.6

Phillips (Captain Smiths Vicat).

Grey Chalk, Sussex (see p. 155)

83 carb. lime .

17 clay

..

Col. Scott, R.B.

Composition of Raw Stone or Raw Material.1

Nature of Lime or

Cement produced.

Description.

Carbonate of Lime and Carbonate of Magnesia.

Clay, Sand, Iron, etc.

Water and

Loss.

Analyst or Authority.

Eminently Hydraulic.

Blue Lias, Lyme Regis (see p. 155)

79.2 carb. lime

17.3 silica and alumina

3.5

Reid.

Some varieties contain less clay.

Carboniferous, Holywell, Wales (Halkin Mountain Limestone), see p. 155

71 .55 carb. lime 1.35 carb. magnesia

72.90

3.5 alumina 2.2 iron.

.8 alkalies 20.l silica

26-6

.5

Muspratt.

Average about 12.5 per cent.

Arden, near Glasgow (see p. 155)

68.0 carb. lime •8 carb. magnesia

68.8

25.8 clay 2.4 iron •6 chlorides

25.8

2.4

Ingram.

Slow Setting Cements. 1

' Heavy English

Portland

3 White Chalk and 1 Clay dried, but unburnt (see p. 160)

77. carb. lime 77.0

2.7 alumina 3.5 iron 15.8 silica 1.0 alkalies

23.0 ....

..

Reid.

Portland Cement, good

58 to 63 carb. lime

21 to 24 silica 5 to 9 alumina 3 to 6 oxide iron 0.5 to 1.5 sulphuric acid

..

Specification of 1'Administration desPontetCliaussees.

Currie & Co.'s circular

Kimmeridge Clay

(Boulogne) (Natural Portland) unbumt

76.6 carb. lime •8 carb. magnesia

77.4

9.2 iron and alumina 13.4 silica

22.6

..

Gilmore.

Native Magnesia (Madras)

99 carb. magnesia.

.5 silic

•5

Dr. Malcomson (Captain Smith's Vicat.)

Moderately Quick Cements.

Dolomite, Portgyfu, North Wales

21.4 carb. lime

61.15 carb. magnesia

82.55

5.58 silica 2.07 alumina 8.76 iron

16-41

1.1

Professor Cabutt (Lipowitz).

Rosendale Cement Stone, Layer No. 9. High Falls, Ulster, New York

43.3 carb. lime

26.0 carb. magnesia

69.3

207 silica and alumina 1*9 iron

2.0 sulphuric acid 4.2 alkaline chlorides

28.8

25.69 iron and alumina. 1.50 sulphuric acid

1.9

Professor Boyntou (Gilmore).

Medina Cement Stone (see p. 158)

47.80 carb. lime 47.80

24.50 silica 51.69

•51

Ingram.

1 For analyses of the burnt Portland cement see p. 227.

Composition of Raw Stone ok Raw Material.1

Nature of Lime or

Cement produced

Description.

Carbonate of Lime and Carbonate of Magnesia.

Clay, Sand, Iron, etc.

Water and Loss.

Analyst or Authority.

Quick Cements.

Roman Cement Stone from Calderwood (Scotland), see p. 159

54.0 carb. lime 14.2 carb. magnesia

68.2

3.4 alumina 13.31 iron 8.8 silica 2.6 phosphates

28.1

37

Professor Penny (Gilmore).

Medina Cement Stone from Portsmouth, Isle of Wight (see p. 15S)

45.32 carb. lime •50 carb. magnesia

45.82

14.15 iron and alumina 1.70 sulphuric acid 37.65 silica

53 50

.68

Roman Cement Stone from Boulogne Septaria

61.6 carb. lime 61.6

4 8 alumina 15.0 silica 9.0 iron

28.8

9.6

Dropping (Captain Smiths Vicat).

Roman Cement Stone from Sheppy Septaria

6.57 carb. lime •5 carb. magnesia

66.2

6.6 alumina 6.8 iron 1.9 manganese 18.0 silica

32 5

1.30

Co.

Rosendale Cement Stone, Layer No. 16, High Falls, New York

46.0 carb. lime 17.8 carb. magnesia

63.8

30.0 silica and alumina 1.3 iron. •2 sulphuric acid 4.l alkaline chlorides

35.6

.7

Professor Boynton (Gilmore).

Rough Tests

A few rough, tests may be applied to a limestone to see if it is likely to furnish a hydraulic lime or cement.

Such a stone will generally have an earthy texture, and will weather to a brown surface.

Acid will not cause upon it so great an effervescence as upon purer limestones.

When breathed upon or moistened a clayey odour is emitted from the stone.

The best plan, however, is to burn a little of the stone in a small experimental kiln, to judge by the slaking, and by the behaviour of pats made from the paste.

1 For analyses of the burnt Roman cement see p. 241.