4.3 Methodology
4.3.1 Sample Collection and Preparation
Samples were collected to represent the production cycle as widely as possible including raw material, dust produced by extraction or processing, and dust from stockpiles of finished product. The exact location within each quarry and type of samples collected varied depending on the individual quarry setup and deposit type, however, samples representing the full production cycle were obtained to ensure sample collection was systematic and comparable among quarries.
Samples were collected using a small plastic spatula and a plastic scoop, to avoid potential contamination from metal implements and with the aid of a natural fibre paint brush to minimize the loss of fines (Figure 4.1a). These implements were cleaned between the collection of individual samples. Where samples of raw material were collected from friable quarry faces, the outer layer of material was removed to expose a fresh surface for sample collection (Figure 4.1b).
Samples of volcanic ash were collected in the field in Montserrat into a pyrex glass dish; a paintbrush was used to eliminate the loss of fine dust when transferring to plastic sample bags. Further samples of volcanic ash were obtained from the collection of Claire Horwell (Durham University). Samples were selected to represent a range of magma types and eruption styles. As rhyolitic eruptions are comparatively rare, ash from only one felsic
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Each bulk dust sample was placed into a Pyrex glass bowl and weighed prior to drying over night at 80oC. The sample was weighed again after drying and then sieved manually for 60 sec. using Endecott stainless steel sieves through >2mm, 1‐2mm and <1mm meshes to remove the non‐ash‐grade particles. Any particles adhered to the mesh were gently brushed off with paint brushes to minimize the loss of fines. Each of the fractions was then weighed, with the <1mm fraction used in most subsequent experiments.
OVERLEAF: Table 4.2 Quarried volcanic dust samples collected. Samples marked § are provided by Noel Worley of British Gypsum and * are samples collected by F. Von Aulock (Liverpool University).
Country Magma Type Deposit Type Quarry Collection Date Details Sample Name
New Zealand
Mafic Lava (hard rock)
Bombay
21/02/09 Fines caught from drillers exhaust BY_01
04/03/09 Drilled fines BY_02
04/03/09 Post blast fines BY_03
04/03/09 Finished product (GAP 7) BY_04
Flat Top 10/03/09 Drilled fines FT_01
10/03/09 Post blast fines FT_02
10/03/09 Finished product: (GAP 25) finest product. FT_03 Puketutu
24/02/09 Drilled fines (fresh, drilled 23/02/09 or 24/02/09) P2_01 24/02/09 Finished product: (GAP 20) screened, blasted 5‐6 months ago P2_02
24/02/09 Post blast particles, quarry floor. P2_03
11/03/09 Post blast fines, quarry floor. P2_04
11/03/09 Drilled fines (pre‐blast) P2_05
Felsic
Pumice (friable, air fall)
Te Puke
19/02/09 Quarry floor, road behind digger wheel TP_01
19/02/09 Quarry Wall, freshly excavated face TP_02
19/02/09 Quarry floor, holding area TP_03
19/02/09 Finished product: (0‐4 mm) screened. TP_04
19/02/09 Quarry Wall, ash layer TP_05
19/02/09 Quarry Wall, pumice layer TP_06
19/02/09 Finished product: finest grade (0‐2mm) TP_07
19/02/09 Pumice piece quarry floor road TP_08
Atiamuri
30/03/09 Perlite from Tram Road near Atiamuri AT_01
30/03/09 Finished product: (1‐4 mm) finest pumice product. AT_02
30/03/09 “cleanfill sand” <1.93 mm AT_03
30/03/09 Finished product: Pumicite (finer grained pumice) AT_04
30/03/09 Finished product: (4‐10 mm) AT_05
Obsidian lava dome
(hard rock) Henderson
Summer 2011 Raw material OBS_01*
Summer 2011 Accumulated dust (on crusher) OBS_02*
Summer 2011 Accumulated dust (on crusher) OBS_03*
Summer 2011 Quarry floor OBS_04*
Country Magma Type Volcano Collection
Date Eruption Style Sample Name
Nicaragua
Mafic
Cerro Negro 01/12/95 Strombolian‐vulcanian eruption (1995) CerNeg*
Italy
Etna 04/11/02 Strombolian eruption (2002) Etna*
Vesuvius 1872 Effusive strombolian eruption (1872) V1872*
1906 Violent strombolian eruption (1906) V1906*
Guatemala Fuego 29/10/74 Sub‐plinian eruption (1974) Fuego*
Iceland Eyjafjallajökull 07/05/10 Effusive fissure eruption Eyja_13*
Montserrat
Intermediate Soufrière Hills
23/01/10 Ash venting eruption (2010) MA_23
28/01/10 Ash venting eruption (2010) MA_28
05/06/99 Dome collapse (1999) Mon_99*
12/07/03 Dome collapse (2003) Mon_03*
Philippines Pinatubo 04/07/91 Plinian eruption (1991) Pina*
Chile Felsic Chaitén 02/05/08 Explosive eruption (2008) Chai_02*
02/05/08 Explosive eruption (2008) Chai_05*
Country Rock Type Quarry Collection
Date Sample Type Sample Name
New Zealand Greywacke Hunua
06/03/09 Finished product: (PAP 5) finest grade. HU_01
09/03/09 Blasted fines HU_02
09/03/09 Drilled fines HU_03
09/03/09 Backbreak fracture (“Waitamata Ash”) HU_04
Great Britain Sandstone Moneystone 09/11 Raw sandstone MSR§
09/11 Finished product MSC§
Table 4.3 Comparative samples of volcanic ash and non‐volcanic quarry dust used in this study. Samples marked * were obtained from the collection of Claire Horwell of Durham University. Samples marked § were provided by Paul Botham of Sibelco, from Moneystone quarry, UK.
Country Magma Type Deposit Type Quarry Collection Date Details Sample Name
Montserrat Intermediate
Pyroclastic density current deposits
(ancient)
Little Bay (Phoenix)
19/01/10 Dust from side of processor (origin: Little Bay) PH_01 19/01/10 Finest grade material (origin: Little Bay) PH_02 23/01/10 Ground, fork by main road to port LB_01
Pyroclastic density current deposits
(modern)
Trants (Eddie’s)
15/01/10 Holding area floor (Tyre tracks) ED_01
15/01/10 Finished product: sand, screened (6mm) quarried Nov ‘09 ED_02 29/01/10 Sand for block making (origin: Trants) BF_01
29/01/10 Rubble/sand from processor floor BF_02
23/01/10 Sand shipped out by Eddie’s (origin: Trants) JN_01 Belham
Valley
01/02/10 Crust off processor BV_01
01/02/10 Ash coasted sand (stockpile surface) BV_02 01/02/10 Non‐ash coated sand (deep within stockpile) BV_03
?/09/07 Sand from stockpile 2007 BV_04
Greece
Felsic
Pumice (friable, air
fall) LAVA
05/07/10 Fine dust from road near processing area LA_01 05/07/10 Raw material from conveyor belt beneath excavated wall LA_02 05/07/10 Finished product: screened (0‐3 mm) finest grade. LA_03 05/07/10 Finished product: screened (0‐8 mm) LA_04
Perlite (friable, hydrated obsidian)
Aegean
08/07/10 Raw material quarry wall AP_01
08/07/10 Finished product: screened (0‐1.2 mm) AP_02 08/07/10 Finished product: screened (0‐3.5 mm) AP_03
08/07/10 Finished product: Isoperl Expanded AP_04
08/07/10 Finished product: Ergoperl Mix AP_05
British
Gypsum Delivered Raw perlite (Milos, Greece) BGRP§
29/01/11 Expanded Perlite (expanded in the UK) BGEP§